port lint should not complain about compressed patch filename extensions

[ryandesign (Ryan Carsten Schmidt)]

port lint --nitpick should not complain about patch filename extensions that portpatch.tcl knows how to decompress on the fly—.Z, .gz, .bz2, .xz:

% port lint --nitpick gelide
--->  Verifying Portfile for gelide
Warning: Patchfile 01-02-update-german-translation.patch.bz2 does not follow the source patch naming policy "*.diff" or "*.patch"
Warning: Patchfile 01-03-update-italian-translation.patch.bz2 does not follow the source patch naming policy "*.diff" or "*.patch"
Warning: Patchfile 01-04-add-generic-spanish-translation.patch.bz2 does not follow the source patch naming policy "*.diff" or "*.patch"
--->  0 errors and 3 warnings found.