[tilegx] A couple of 32/64bit cleanup.
[tilegx] Fix a typo.
[tilegx] fixed a couple of bugs.

  * UntagAndJumpIfNotSmi/UntagAndJumpIfSmi logic error.
  * PointerSize should be 8 for TileGX.
[tilegx] Fixed one bit shift bug in GenerateDictionaryStore stub.