Frontend: Pull CodeGenAction out more, and eliminate CreateBackendConsumer.

This is the way I would like to move the frontend function towards -- distinct
pieces of functionality should be exposed only via FrontendAction
implementations which have clean and relatively-stable APIs.

This also isolates the surface area in clang which depends on LLVM CodeGen.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97110 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed