Enable more compile warnings

and fix the fallout detected.

meson.build

@@ -40,7 +40,6 @@ test_c_args = [
   '-Wdate-time',
   '-Wdeclaration-after-statement',
   ['-Werror=format-security', '-Werror=format=2'],
-  '-Wextra',
   '-Wendif-labels',
   '-Werror=incompatible-pointer-types',
   '-Werror=missing-declarations',
@@ -48,11 +47,13 @@ test_c_args = [
   '-Werror=return-type',
   '-Werror=shift-count-overflow',
   '-Werror=shift-overflow=2',
+  '-Werror=implicit-fallthrough=3',
   '-Wfloat-equal',
   '-Wformat-nonliteral',
   '-Wformat-security',
   '-Winit-self',
   '-Wmaybe-uninitialized',
+  '-Wmissing-field-initializers',
   '-Wmissing-include-dirs',
   '-Wmissing-noreturn',
   '-Wnested-externs',
@@ -67,6 +68,7 @@ test_c_args = [
   '-Wstrict-prototypes',
   '-Wswitch-default',
   '-Wswitch-enum',
+  '-Wtype-limits',
   '-Wundef',
   '-Wunused-function',
 ]