getprogname: Move declaration from "getprogname.h" to <stdlib.h>.
* lib/stdlib.in.h (getprogname): New declaration.
* lib/getprogname.h: Add deprecation warning.
(getprogname): Remove declaration.
* lib/getprogname.c: Include <stdlib.h> instead of getprogname.h.
* m4/stdlib_h.m4 (gl_STDLIB_H): Test whether getprogname is declared.
(gl_STDLIB_H_REQUIRE_DEFAULTS): Initialize GNULIB_GETPROGNAME.
(gl_STDLIB_H_DEFAULTS): Initialize HAVE_GETPROGNAME.
* m4/getprogname.m4 (gl_PREREQ_GETPROGNAME): New macro, extracted from
gl_FUNC_GETPROGNAME. Set HAVE_GETPROGNAME.
(gl_FUNC_GETPROGNAME): Remove code that was moved to
gl_PREREQ_GETPROGNAME.
* modules/stdlib (Makefile.am): Substitute GNULIB_GETPROGNAME and
HAVE_GETPROGNAME.
* modules/getprogname (Depends-on): Add stdlib.
(configure.ac): Define a module indicator. Invoke gl_PREREQ_GETPROGNAME.
(Makefile.am): Don't compile getprogname.c if not needed.
(Include): List <stdlib.h> instead of getprogname.h.
* tests/test-getprogname.c: Include <stdlib.h> instead of getprogname.h.
* NEWS: Mention the change.
* lib/argmatch.c: Don't include getprogname.h.
* lib/c-stack.c: Likewise.
* lib/error.c: Likewise.
* lib/git-merge-changelog.c: Likewise.