[PATCH] Add address space argument to allowsUnalignedMemoryAccess.

[Matt Arsenault]

  The reason I swapped the order was because the address space could be necessary for correctness, but Fast in principle could always be optional. When updating the uses of it, more places required throwing in a null pointer for Fast just to specify the address space rather than the other way around.

http://llvm-reviews.chandlerc.com/D2522