Handle implicitly-included PCH files the same way as

implicitly-included PTH files during initialization, delaying the
mapping down to the "original source file" until after later in the
initialization process.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166452 91177308-0d34-0410-b5e6-96231b3b80d8