calloc-gnu: Allow use as dependency from test modules.
* m4/calloc.m4 (gl_FUNC_CALLOC_GNU): Set REPLACE_CALLOC_FOR_CALLOC_GNU
instead of REPLACE_CALLOC.
(gl_FUNC_CALLOC_POSIX): Set REPLACE_CALLOC_FOR_CALLOC_POSIX instead of
REPLACE_CALLOC.
* m4/stdlib_h.m4 (gl_STDLIB_H_REQUIRE_DEFAULTS): Initialize the
calloc-gnu module indicator.
(gl_STDLIB_H_DEFAULTS): Initialize REPLACE_CALLOC_FOR_CALLOC_GNU,
REPLACE_CALLOC_FOR_CALLOC_POSIX, not REPLACE_CALLOC.
* modules/stdlib (Makefile.am): Substitute GNULIB_CALLOC_GNU,
REPLACE_CALLOC_FOR_CALLOC_GNU, REPLACE_CALLOC_FOR_CALLOC_POSIX, not
REPLACE_CALLOC.
* modules/calloc-posix (Depends-on, configure.ac): Test
REPLACE_CALLOC_FOR_CALLOC_POSIX instead of REPLACE_CALLOC.
* modules/calloc-gnu (Depends-on): Add xalloc-oversized.
(configure.ac): Test REPLACE_CALLOC_FOR_CALLOC_GNU instead of
REPLACE_CALLOC. Set a module indicator.
* lib/stdlib.in.h (calloc): Test REPLACE_CALLOC_FOR_CALLOC_POSIX,
REPLACE_CALLOC_FOR_CALLOC_GNU, and the respective module indicators
instead of just REPLACE_CALLOC.