* gnulib/progname.h: Likewise.
* conf/i386-pc.rmk (grub_mkimage_SOURCES): Add `gnulib/progname.c'.
* util/i386/pc/grub-mkimage.c: Include `"progname.h"'.
(usage): Replace `progname' with `program_name'.
(main): Use set_program_name() for program name initialization.
Fix build for systems without error().
* gnulib/error.c: New file (imported from Gnulib).
* gnulib/error.h: Likewise.
* conf/common.rmk (grub_mkisofs_SOURCES): Add `gnulib/error.c'.
* util/mkisofs/mkisofs.c (program_name): Remove `static' qualifier
(this variable is now used by error()).