This change adds some [self own_clipboard] calls in the necessary places to get the proper greedy behavior.
UTF8_STRING and STRING properties seem to work well now with the test cases (PRIMARY, and CLIPBOARD). I can copy from several different X apps, and have the behavior be correct when pasting. I also verified that quartz-wm isn't doing the copying, by disabling the quartz-wm paths.
(cherry picked from commit 934669f732)
