Check pointer types for arguments of Neon load/store macros. rdar://9958031

The Neon load/store intrinsics need to be implemented as macros to avoid
hiding alignment attributes on the pointer arguments, and the macros can
only evaluate those pointer arguments once (in case they have side effects),
so it has been hard to get the right type checking for those pointers.
I tried various alternatives in the arm_neon.h header, but it's much more
straightforward to just check directly in Sema.

llvm-svn: 144075