build: Avoid trouble on mingw caused by mingw's *printf functions.
Reported by Michele Locati <michele@locati.it>
in <https://lists.gnu.org/archive/html/bug-gettext/2019-05/msg00103.html>.
* gettext-runtime/intl/Makefile.am (AM_CPPFLAGS): Define __USE_MINGW_ANSI_STDIO
to 0.
* gettext-runtime/libasprintf/Makefile.am (DEFS): Likewise.
* libtextstyle/lib/Makefile.am (AM_CPPFLAGS): Likewise.
