intl: Fix bug in the exported *wprintf functions.

intl: Fix bug in the exported *wprintf functions.

* autogen.sh (GNULIB_MODULES_LIBINTL): Add vasnwprintf-posix.
* gettext-runtime/intl/configure.ac: Hide the symbols from the gnulib modules
isnand-nolibm, isnanl-nolibm, printf-frexp, printf-frexpl, signbit, vasnwprintf,
frexp-nolibm, frexpl-nolibm.
* gettext-runtime/intl/printf.c: Don't instantiate the vasnwprintf code here.
* gettext-runtime/intl/wprintf-parse.h: Remove file, moved to gnulib.
* gettext-runtime/intl/vasnwprintf.h: Remove file, moved to gnulib.
* gettext-runtime/intl/Makefile.am (EXTRA_DIST): Remove wprintf-parse.h,
vasnwprintf.h.
(printf.lo): Simplify dependencies accordingly.