We pull file names out of the clang infrastructure to match where
classes are defined. We use the file name to pull comments and find
and process Trick header comments. Up to now clang gave us the realpath
of files and when we looked up comments we already had the realpath and
everything worked. In clang 3.6 in some places we are not getting the
realpath anymore which confuses ICG. Added code to get the realpath of
any file name we use throughout the code.
refs #167
