man: Add versions where build flag features were added

This makes it easier for users to understand how long these features
have been supported for, and whether backward compatibility might be
needed.

man/dpkg-buildflags.pod

@@ -70,6 +70,7 @@ Override the flag named I<flag> to have the value I<value>.
 =item B<STRIP> I<flag> I<value>
 
 Strip from the flag named I<flag> all the build flags listed in I<value>.
+Since dpkg 1.16.1.
 
 =item B<APPEND> I<flag> I<value>
 
@@ -80,6 +81,7 @@ A space is prepended to the appended value if the flag's current value is non-em
 
 Extend the flag named I<flag> by prepending the options given in I<value>.
 A space is appended to the prepended value if the flag's current value is non-empty.
+Since dpkg 1.16.1.
 
 =back
 
@@ -275,10 +277,12 @@ Options for the C++ compiler. Same as B<CFLAGS>.
 =item B<OBJCFLAGS>
 
 Options for the Objective C compiler. Same as B<CFLAGS>.
+Since dpkg 1.17.7.
 
 =item B<OBJCXXFLAGS>
 
 Options for the Objective C++ compiler. Same as B<CXXFLAGS>.
+Since dpkg 1.17.7.
 
 =item B<GCJFLAGS>
 
@@ -295,6 +299,7 @@ Options for the Fortran 77 compiler. A subset of B<CFLAGS>.
 =item B<FCFLAGS>
 
 Options for the Fortran 9x compiler. Same as B<FFLAGS>.
+Since dpkg 1.17.7.
 
 =item B<LDFLAGS>
 
@@ -337,8 +342,9 @@ reasons.
 
 =item B<lfs>
 
-This setting (disabled by default) enables Large File Support on 32-bit
-architectures where their ABI does not include LFS by default, by adding
+This setting (since dpkg 1.10.0; disabled by default) enables
+Large File Support on 32-bit architectures where their ABI does
+not include LFS by default, by adding
 B<-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64> to B<CPPFLAGS>.
 
 =back
@@ -352,8 +358,9 @@ problems in the source code or build system.
 
 =item B<bug>
 
-This setting (disabled by default) adds any warning option that reliably
-detects problematic source code. The warnings are fatal.
+This setting (since dpkg 1.17.4; disabled by default) adds any warning
+option that reliably detects problematic source code.
+The warnings are fatal.
 The only currently supported flags are B<CFLAGS> and B<CXXFLAGS>
 with flags set to B<-Werror=array-bounds>, B<-Werror=clobbered>,
 B<-Werror=implicit-function-declaration> and
@@ -361,9 +368,10 @@ B<-Werror=volatile-register-var>.
 
 =item B<canary>
 
-This setting (disabled by default) adds dummy canary options to the build
-flags, so that the build logs can be checked for how the build flags
-propagate and to allow finding any omission of normal build flag settings.
+This setting (since dpkg 1.17.14; disabled by default) adds dummy canary
+options to the build flags, so that the build logs can be checked for how
+the build flags propagate and to allow finding any omission of normal
+build flag settings.
 The only currently supported flags are B<CPPFLAGS>, B<CFLAGS>,
 B<OBJCFLAGS>, B<CXXFLAGS> and B<OBJCXXFLAGS> with flags set
 to B<-D__DEB_CANARY_>I<flag>_I<random-id>B<__>, and
@@ -402,24 +410,28 @@ even functionality.
 
 =item B<address>
 
-This setting (disabled by default) adds B<-fsanitize=address> to
+This setting (since dpkg 1.18.0; disabled by default) adds
+B<-fsanitize=address> to
 B<LDFLAGS> and B<-fsanitize=address -fno-omit-frame-pointer> to
 B<CFLAGS> and B<CXXFLAGS>.
 
 =item B<thread>
 
-This setting (disabled by default) adds B<-fsanitize=thread> to
+This setting (since dpkg 1.18.0; disabled by default) adds
+B<-fsanitize=thread> to
 B<CFLAGS>, B<CXXFLAGS> and B<LDFLAGS>.
 
 =item B<leak>
 
-This setting (disabled by default) adds B<-fsanitize=leak> to
+This setting (since dpkg 1.18.0; disabled by default) adds
+B<-fsanitize=leak> to
 B<LDFLAGS>. It gets automatically disabled if either the B<address>
 or the B<thread> features are enabled, as they imply it.
 
 =item B<undefined>
 
-This setting (disabled by default) adds B<-fsanitize=undefined> to
+This setting (since dpkg 1.18.0; disabled by default) adds
+B<-fsanitize=undefined> to
 B<CFLAGS>, B<CXXFLAGS> and B<LDFLAGS>.
 
 =back
@@ -436,7 +448,7 @@ that support them.
 
 =item B<format>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.16.1; enabled by default) adds
 B<-Wformat -Werror=format-security>
 to B<CFLAGS>, B<CXXFLAGS>, B<OBJCFLAGS> and B<OBJCXXFLAGS>.
 This will warn about improper format
@@ -450,7 +462,7 @@ input and contains ‘%n’.
 
 =item B<fortify>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.16.1; enabled by default) adds
 B<-D_FORTIFY_SOURCE=2>
 to B<CPPFLAGS>. During code generation the compiler
 knows a great deal of information about buffer sizes (where possible), and
@@ -468,8 +480,8 @@ glibc 2.16 and later.
 
 =item B<stackprotector>
 
-This setting (enabled by default if stackprotectorstrong is not in use) adds
-B<-fstack-protector --param=ssp-buffer-size=4>
+This setting (since dpkg 1.16.1; enabled by default if stackprotectorstrong
+is not in use) adds B<-fstack-protector --param=ssp-buffer-size=4>
 to B<CFLAGS>, B<CXXFLAGS>, B<OBJCFLAGS>, B<OBJCXXFLAGS>,
 B<GCJFLAGS>, B<FFLAGS> and B<FCFLAGS>.
 This adds safety checks against stack
@@ -484,7 +496,7 @@ B<-nostdlib> or B<-ffreestanding> or similar.
 
 =item B<stackprotectorstrong>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.17.11; enabled by default) adds
 B<-fstack-protector-strong>
 to B<CFLAGS>, B<CXXFLAGS>, B<OBJCFLAGS>, B<OBJCXXFLAGS>,
 B<GCJFLAGS>, B<FFLAGS> and B<FCFLAGS>.
@@ -498,7 +510,7 @@ addition also requires gcc 4.9 and later.
 
 =item B<relro>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.16.1; enabled by default) adds
 B<-Wl,-z,relro>
 to B<LDFLAGS>.  During program load, several ELF memory sections need
 to be written to by the linker. This flags the loader to turn these
@@ -508,7 +520,7 @@ B<bindnow> will become disabled as well.
 
 =item B<bindnow>
 
-This setting (disabled by default) adds
+This setting (since dpkg 1.16.1; disabled by default) adds
 B<-Wl,-z,now>
 to B<LDFLAGS>. During program load, all dynamic symbols are resolved,
 allowing for the entire PLT to be marked read-only (due to B<relro>
@@ -516,7 +528,8 @@ above). The option cannot become enabled if B<relro> is not enabled.
 
 =item B<pie>
 
-This setting (with no global default since dpkg 1.18.23, as it is enabled
+This setting (since dpkg 1.16.1; with no global default since dpkg 1.18.23,
+as it is enabled
 by default now by gcc on the amd64, arm64, armel, armhf, hurd-i386, i386,
 kfreebsd-amd64, kfreebsd-i386, mips, mipsel, mips64el, powerpc, ppc64,
 ppc64el, riscv64, s390x, sparc and sparc64 Debian architectures) adds
@@ -604,7 +617,7 @@ architectures that support them.
 
 =item B<timeless>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.17.14; enabled by default) adds
 B<-Wdate-time>
 to B<CPPFLAGS>.
 This will cause warnings when the B<__TIME__>, B<__DATE__> and
@@ -612,7 +625,7 @@ B<__TIMESTAMP__> macros are used.
 
 =item B<fixfilepath>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.19.1; enabled by default) adds
 B<-ffile-prefix-map=>I<BUILDPATH>B<=.>
 to B<CFLAGS>, B<CXXFLAGS>, B<OBJCFLAGS>, B<OBJCXXFLAGS>,
 B<GCJFLAGS>, B<FFLAGS> and B<FCFLAGS> where B<BUILDPATH> is
@@ -631,7 +644,7 @@ The ideal fix is to stop capturing build flags.
 
 =item B<fixdebugpath>
 
-This setting (enabled by default) adds
+This setting (since dpkg 1.18.5; enabled by default) adds
 B<-fdebug-prefix-map=>I<BUILDPATH>B<=.>
 to B<CFLAGS>, B<CXXFLAGS>, B<OBJCFLAGS>, B<OBJCXXFLAGS>,
 B<GCJFLAGS>, B<FFLAGS> and B<FCFLAGS> where B<BUILDPATH> is
@@ -656,14 +669,14 @@ by package maintainers to change the resulting build flags.
 
 =item B<DEB_>I<flag>B<_SET>
 
-=item B<DEB_>I<flag>B<_MAINT_SET>
+=item B<DEB_>I<flag>B<_MAINT_SET> (since dpkg 1.16.1)
 
 This variable can be used to force the value returned for the given
 I<flag>.
 
-=item B<DEB_>I<flag>B<_STRIP>
+=item B<DEB_>I<flag>B<_STRIP> (since dpkg 1.16.1)
 
-=item B<DEB_>I<flag>B<_MAINT_STRIP>
+=item B<DEB_>I<flag>B<_MAINT_STRIP> (since dpkg 1.16.1)
 
 This variable can be used to provide a space separated list of options
 that will be stripped from the set of flags returned for the given
@@ -671,21 +684,21 @@ I<flag>.
 
 =item B<DEB_>I<flag>B<_APPEND>
 
-=item B<DEB_>I<flag>B<_MAINT_APPEND>
+=item B<DEB_>I<flag>B<_MAINT_APPEND> (since dpkg 1.16.1)
 
 This variable can be used to append supplementary options to the value
 returned for the given I<flag>.
 
-=item B<DEB_>I<flag>B<_PREPEND>
+=item B<DEB_>I<flag>B<_PREPEND> (since dpkg 1.16.1)
 
-=item B<DEB_>I<flag>B<_MAINT_PREPEND>
+=item B<DEB_>I<flag>B<_MAINT_PREPEND> (since dpkg 1.16.1)
 
 This variable can be used to prepend supplementary options to the value
 returned for the given I<flag>.
 
 =item B<DEB_BUILD_OPTIONS>
 
-=item B<DEB_BUILD_MAINT_OPTIONS>
+=item B<DEB_BUILD_MAINT_OPTIONS> (since dpkg 1.16.1)
 
 These variables can be used by a user or maintainer to disable/enable
 various area features that affect build flags.