[SROA] Add support for non-integral pointers

Summary: C.f. http://llvm.org/docs/LangRef.html#non-integral-pointer-type

Reviewers: chandlerc, loladiro

Reviewed By: loladiro

Subscribers: reames, loladiro, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D32203

llvm-svn: 305639