[tilegx] Implement more hooks & we get initial v8 testsuite result.

  Implement more hooks which is necessary as they are triggered by
various test cases in v8 testsuite.

  currently, we got initial v8 testsuite result:

   [131:02|% 100|+ 5574|- 4149]: Done
     ^              ^       ^
     |              |       |
     |              |       |
     |              |       |
     |              |       |
     |              Pass    Fail
     |
     |
   Time: minutes
[tilegx] Fix one register collision bug.

  The macro "Push" will implicitly use "at" as temp reg, so we should
use "at2" near "Push" to avoid reg collision.
[tilegx] Cleanup "JumpLabelToJumpRegister".

  Currently, TileGX always use indirect jump, so no need of this
"JumpLabelToJumpRegister". But we still check if it's needed in case
there are something happened unexpectedly.