maint: address sc_bindtextdomain, sc_program_name and sc_prohibit_HAVE_MBRTOWC.

* bootstrap.conf (gnulib_modules): Require progname.
	* src/complain.c, src/getargs.c, src/getargs.h, src/main.c: Use it.
	* cfg.mk (exclude): New.
	Use it.
	Skip lib/main.c for bindtextdomain and set_program_name.

lib/.gitignore

@@ -264,3 +264,5 @@
 /fpending.c
 /fpending.h
 /sysexits.in.h
+/progname.c
+/progname.h