bitcoin/bitcoin — pull request #1847 by gavinandresen (2012-09-21 19:46:17+00:00)
Title: Compile/link Bitcoin-Qt.app with -pthread on OSX

There was a report of a mysterious crash on OSX 10.7 that may or may not be caused by this. In any case, Bitcoin-Qt is multi-threaded, so compiling with -pthread is the right thing to do.