printf-gnu: New module.

* m4/printf-posix.m4: Renamed from m4/printf-posix-rpl.m4.
(gl_FUNC_PRINTF_IS_POSIX): New macro.
(gl_FUNC_PRINTF_POSIX): Require it. Don't require
gl_FUNC_VFPRINTF_POSIX. Invoke gl_PREREQ_VASNPRINTF_WITH_POSIX_EXTRAS
and gl_REPLACE_VASNPRINTF.
* m4/printf-gnu.m4: New file, based on m4/fprintf-posix.m4.
* modules/printf-posix (Files): Update.
* modules/printf-gnu: New file, based on modules/vasnprintf-gnu.
* doc/posix-functions/printf.texi: Mention the new module.

modules/printf-gnu

@@ -0,0 +1,29 @@
+Description:
+POSIX and GNU compatible printf() function: print formatted output to
+standard output
+
+Comment:
+This module should not be used as a dependency from a test module,
+otherwise when this module occurs as a tests-related module, it will
+have side effects on the compilation of the 'vasnprintf' module, if
+that module occurs among the main modules in lib/.
+
+Files:
+m4/printf-gnu.m4
+
+Depends-on:
+printf-posix
+
+configure.ac:
+gl_FUNC_PRINTF_GNU
+
+Makefile.am:
+
+Include:
+<stdio.h>
+
+License:
+LGPL
+
+Maintainer:
+all