OSX defines _POSIX_THREAD_PROCESS_SHARED but does not actually support it.
Review Request #102145 - Created July 30, 2011 and submitted
_POSIX_THREAD_PROCESS_SHARED is defined on OSX as of Snow Leopard, but the functionality doesn't actually work. This leads to hangs in all KDE apps on OSX, so this change makes sure _POSIX_THREAD_PROCESS_SHARED is not used on OSX.
Built and tested on OSX Snow Leopard and Lion.