This is the first step to making all DIScopes have a common metadata prefix (so
that things (using directives, for example) that can appear in any scope can be
added to that common prefix). DIFile is itself a DIScope so the common prefix
of all DIScopes cannot be a DIFile - instead it's the raw filename/directory
name pair.
llvm-svn: 177239
This is the next step towards making the metadata for DIScopes have a common
prefix rather than having to delegate based on their tag type.
llvm-svn: 176913
David Blaikie