Remove localtime_tz and strftime_tz.

This also brings our copy of strftime.c much closer to upstream, though
we still have several GNU extensions and hacks to deal with Android32's
broken time_t.

Bug: 15765976
Change-Id: Ic9ef36e8acd3619504ecc4d73feec2b61fd4dfa1
Merge "Remove localtime_tz and strftime_tz."