Add _tzset_unlocked and _tzset_unlocked_r

Add _tzset_unlocked and _tzset_unlocked_r

newlib:

	* libc/time/local.h (_tzset_unlocked_r): Add prototype.
	(_tzset_unlocked): Ditto.
	* libc/time/tzset.c (_tzset_unlocked): New function, call
	_tzset_unlocked_r.
	(tzset): Lock and call _tzset_unlocked_r.
	* libc/time/tzset_r (_tzset_unlocked_r): Remove locking and rename
	from _tzset_r.
	(_tzset_r): Lock and call _tzset_unlocked_r.

cygwin:

	* localtime.cc (tzset_unlocked): Export as _tzset_unlocked.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>