pthread_sigmask, timer-time: use gl_THREADLIB only if needed
Without this fix, Emacs would sometimes call sigprocmask instead
of pthread_sigmask, which is a no-no in multithreaded applications.
Problem reported by Jorgen Schaefer in <http://bugs.gnu.org/17561>.
* m4/pthread_sigmask.m4 (gl_FUNC_PTHREAD_SIGMASK):
Suppress check for pthread_sigmask working without -lpthread if
the application always links with -lpthread. Do not link with
$LIBMULTITHREAD if gl_THREADLIB is not defined.
* m4/timer_time.m4 (gl_TIMER_TIME):
Require gl_THREADLIB only if it is defined. Do not append
$LIBMULTITHREAD to LIB_TIMER_TIME if gl_THREADLIB is not defined.