Revert "Add lib/Codgen/[CGRTTI|MicrosoftRTTI].cpp to CMakeLists.txt (r212445)"

I misidentified the problem and did not test suffifiently. The files had
correctly been removed, but for some reason they still remained in my git
checkout. Not adding the files back to CMakeLists.txt, but rather removing
the stale files was the solution. Sorry for the unnecessary noise.