c32rtomb: Add a sanity check, working around Solaris 11 OmniOS. * m4/c32rtomb.m4 (gl_CHECK_FUNC_C32RTOMB): New macro, extracted from gl_FUNC_C32RTOMB. (gl_C32RTOMB_SANITYCHECK): New macro. (gl_FUNC_C32RTOMB): Require gl_CHECK_FUNC_C32RTOMB and gl_C32RTOMB_SANITYCHECK. If HAVE_WORKING_C32RTOMB is 0, set REPLACE_C32RTOMB. * lib/c32rtomb.c (c32rtomb): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * m4/mbrtoc32.m4 (gl_PREREQ_MBRTOC32): Require gl_C32RTOMB_SANITYCHECK. * lib/mbrtoc32.c (mbrtoc32): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * modules/mbrtoc32 (Files): Add m4/c32rtomb.m4. * lib/btoc32.c (btoc32): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * lib/mbsrtoc32s.c: Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * lib/mbsnrtoc32s.c: Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * lib/c32tob.c (c32tob): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * modules/c32tob (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * lib/c32srtombs.c: Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * lib/c32snrtombs.c: Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * lib/c32is-impl.h (FUNC): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * modules/c32isalnum (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isalpha (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isblank (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32iscntrl (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isdigit (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isgraph (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32islower (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isprint (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32ispunct (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isspace (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isupper (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32isxdigit (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * lib/c32to-impl.h (FUNC): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * modules/c32tolower (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * modules/c32toupper (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK. * lib/c32width.c (c32width): Together with HAVE_WORKING_MBRTOC32, test also HAVE_WORKING_C32RTOMB. * modules/c32width (Files): Add m4/c32rtomb.m4. (configure.ac): Require gl_C32RTOMB_SANITYCHECK.