Revert r211402 (and r211408,r211410), "CodeGen: Refactor dynamic_cast and typeid" It crashes msvc codegen in clang/test/SemaCXX/undefined-internal.cpp.

It is reproducible with:

  $ clang -cc1 -triple i686-win32 -emit-llvm-only clang/test/SemaCXX/undefined-internal.cpp