clang-cl: Implement the /Tc, /TC, /Tp and /TP options.

These are used to specify source files, and whether to treat source
files as C or C++.

Differential Revision: http://llvm-reviews.chandlerc.com/D1290

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187760 91177308-0d34-0410-b5e6-96231b3b80d8