build: Take advantage of gcc warning options not included in -Wall.
* autogen.sh (GNULIB_MODULES_RUNTIME_OTHER, GNULIB_MODULES_LIBINTL,
GNULIB_MODULES_LIBASPRINTF, GNULIB_MODULES_TOOLS_OTHER): Add manywarnings.
* m4/more-warnings.m4: New file.
* libtextstyle/autogen.sh (GNULIB_MODULES): Add manywarnings.
Copy also more-warnings.m4.
* gnulib-local/modules/libxml (Makefile.am): New variable libxml_rpl_la_CFLAGS.
* libtextstyle/gnulib-local/modules/libcroco (Makefile.am): New variable
libcroco_rpl_la_CFLAGS.
* libtextstyle/gnulib-local/modules/libglib (Makefile.am): New variable
libglib_rpl_la_CFLAGS.
* libtextstyle/configure.ac: Invoke gt_MORE_WARNINGS, gl_CC_INHIBIT_WARNINGS.
* libtextstyle/lib/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
(config.h): Do the compilations with GL_CFLAG_INHIBIT_WARNINGS.
* gettext-runtime/configure.ac: Invoke gt_MORE_WARNINGS.
* gettext-runtime/src/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
* gnulib-local/modules/gettext-runtime-misc (Makefile.am): Add WARN_CFLAGS to
AM_CFLAGS.
* gettext-runtime/intl/configure.ac: Invoke gt_MORE_WARNINGS.
* gettext-runtime/intl/Makefile.am (AM_CFLAGS): Add WARN_CFLAGS.
* gnulib-local/modules/gettext-runtime-intl-misc (Makefile.am): Add WARN_CFLAGS
to AM_CFLAGS.
* gettext-runtime/libasprintf/configure.ac: Invoke gt_MORE_WARNINGS.
* gettext-runtime/libasprintf/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
* gettext-tools/configure.ac: Invoke gt_MORE_WARNINGS, gl_CC_INHIBIT_WARNINGS.
* gettext-tools/gnulib-lib/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
* gettext-tools/libgrep/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
* gettext-tools/src/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
* gettext-tools/libgettextpo/Makefile.am (AM_CFLAGS): Set to WARN_CFLAGS.
(config.h): Do the compilations with GL_CFLAG_INHIBIT_WARNINGS.
