Moved all clients of Diagnostics to use FullSourceLoc instead of SourceLocation.
Added many utility methods to FullSourceLoc to provide shorthand for:

    FullLoc.getManager().someMethod(FullLoc.getLocation());
    
instead we have:

    FullLoc.someMethod();
    
Modified TextDiagnostics (and related classes) to use this short-hand.

llvm-svn: 44957