Fix warnings for functions introduced in Android API level 12.
Reported by Po Lu <luangruo@yahoo.com>.
* m4/ftruncate.m4 (gl_FUNC_FTRUNCATE): Test for ftruncate using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/glob.m4 (gl_PREREQ_GLOB): Test for getpwnam_r using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/nproc.m4 (gl_PREREQ_NPROC): Test for sched_getaffinity using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS.
* m4/pread.m4 (gl_FUNC_PREAD): Test for pread using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/pwrite.m4 (gl_FUNC_PWRITE): Test for pwrite using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/thread.m4 (gl_THREAD): Test for pthread_atfork using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS.
* m4/timegm.m4 (gl_FUNC_TIMEGM): Test for timegm using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/utimensat.m4 (gl_FUNC_UTIMENSAT): Test for utimensat using
gl_CHECK_FUNCS_ANDROID instead of AC_CHECK_FUNCS_ONCE.
* m4/utimens.m4 (gl_UTIMENS): Likewise.