Fix a crash involving pointer-to-data-members of boolean type. We were

constructing an LLVM PointerType directly from the "bool"'s LLVM type
(i1), which resulted in unfortunate pointer type i1*. The fix is to
build the LLVM PointerType from the corresponding Clang PointerType,
so that we get i8* in the case of a bool. 

John, please review. I also left a FIXME there because we seem to be
dropping "volatile", which would be rather unfortunate.

llvm-svn: 112819