Simplify some timezone code.

Since we only allow GMT as a timezone and ignore what the browser
says, we can simplify a lot of this code.
Revert "reimplement getCurrentTime"

This reverts commit bd615f6f4499cc2b928c5603ba98d6bd689e608e.
Merge pull request #1582 from waywardmonkeys/simplify-timezone

Simplify timezone
restore ZTVN10 hacks, but only for non-ta2 where we do not link in libcxxabi
Merge pull request #1587 from inolen/openal_buffers_revert

revert pr #1493
Merge branch 'incoming' of https://github.com/kripken/emscripten into hp-beta