Made the mechanism of defining preprocessor defs for maxint, ptrdiff_t, wchar

etc more generic. For some targets, long may not be equal to pointer size. For
example: PIC16 has int as i16, ptr as i16 but long as i32.

Also fixed a few build warnings in assert() functions in CFRefCount.cpp,
CGDecl.cpp, SemaDeclCXX.cpp and ParseDeclCXX.cpp.

llvm-svn: 58501