Extend -remap-file=from;to to permit mapping from a non-existent
file. This is accomplished by introducing the notion of a "virtual"
file into the file manager, which provides a FileEntry* for a named
file whose size and modification time are known but which may not
exist on disk.

Added a cute little test that remaps both a .c file and a .h file it
includes to alternative files.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90329 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed