[modules] Load .pcm files specified by -fmodule-file lazily.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220731 91177308-0d34-0410-b5e6-96231b3b80d8
Use the newer/simple API for passing a diagnostic handler to the IR linker.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220733 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused variable.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220738 91177308-0d34-0410-b5e6-96231b3b80d8
Improve on the diagnostic in my last patch and change warning
to error. rdar://18768214.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220740 91177308-0d34-0410-b5e6-96231b3b80d8