* acinclude.m4: Change C9X references to refer to C99. * aclocal.m4, configure: Regenerate. * config/os/gnu-linux/bits/os_defines.h, src/complex.cc, testsuite/22_locale/codecvt_wchar_t_char.cc, include/bits/stl_config.h, include/c/bits/std_cwchar.h, libmath/mathconf.h: Change C9X references to refer to C99. From-SVN: r37743