Provides a way to merge multiple vfs::FileSystem objects into a single filesystem. llvm-svn: 201635
This adds the minimum virtual file system support to start migrating FileManager onto the VFS. Originally discussed here: http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-February/035188.html Differential Revision: http://llvm-reviews.chandlerc.com/D2745 llvm-svn: 201618