stdbit: don’t assume -DHAVE_CONFIG_H This is needed for diffutils, which doesn’t define HAVE_CONFIG_H. There needs to be some way for a test shared with glibc to discover whether it should use the Gnulib or the glibc testing framework, and I guess this is it. * modules/stdbit-tests (GNULIB_TEST_STDBIT): Define. * tests/tst-stdbit.h: Use GNULIB_TEST_STDBIT, not HAVE_CONFIG_H.