Remove some dead code.

Patch by Stephen Lin!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177490 91177308-0d34-0410-b5e6-96231b3b80d8
Work-in-progress documentation on the experimental modules feature.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177491 91177308-0d34-0410-b5e6-96231b3b80d8