Figure out what to do with third_party paths

[marco-c]

[marco-c]

One possibility would be to ignore them completely, another possibility would be to merge them (e.g. any modification to any file in gfx/cairo/ would be considered as a modification to gfx/cairo/), or the last possibility is to consider them as any other path.

One of the problems with third-party updates is that they contain both enhancements, fixes, regression fixes.