* aclocal.m4 (AC_LANG_PROGRAM): New macro.  Overrides stock
        AC_LANG_PROGRAM from autoconf.
        (grub_ASM_USCORE, grub_PROG_OBJCOPY_ABSOLUTE): Add missing      
        prototypes (fixes warning).

        * configure.ac: Add `-Werror' to TARGET_CFLAGS unless
        `--disable-werror' was used.