Revert "CodeGen: Properly null-check typeid expressions"

This reverts commit r213401, r213402, r213403, and r213404.

I accidently committed these changes instead of updating the
differential.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213405 91177308-0d34-0410-b5e6-96231b3b80d8