gettimeofday, tzset: Respect rules for use of AC_LIBOBJ. * modules/tzset (configure.ac): Don't invoke gl_FUNC_TZSET_CLOBBER, just gl_FUNC_TZSET. * m4/tzset.m4 (gl_FUNC_TZSET): New macro. (gl_FUNC_TZSET_CLOBBER): Remove actions. * m4/gettimeofday.m4 (gl_FUNC_GETTIMEOFDAY): Invoke gl_FUNC_TZSET_CLOBBER and its actions here, if present.