[PATCH] Teach MemoryBuiltins about address spaces

[Nuno Lopes]

  I'm not sure this patch is correct.
  I assume you cannot mix pointers from different address spaces (e.g., a PHI of 2 pointer of different address spaces).  Even if you can, the pointer sizes will have to be of the same size.  Therefore, i don't think we need to track the pointer size everywhere, since it will have the be same everywhere.
  Moreover, if there could be a mix of pointer sizes, the current code wouldn't handle that situation.  We would need some ZExts to put all integers into the same size when combining them (e.g., in a phi node).

http://llvm-reviews.chandlerc.com/D1463