This patch extends the previous patch by starting to incorporate more...

This patch extends the previous patch by starting to incorporate more functionality, like lookup-by-name and exporting lookup tables, into the module manager.  Methods now have documentation.  A few more functions have been switched over to the new iterator style and away from manual/explicit iteration.  Ultimately we want to move away from name lookup here, as symlinks make filenames not a safe unique value, but we use it here as a stopgap before better measures are in place (namely instead using FileEntry* from a global FileManager).

llvm-svn: 136107