maccore: fixed MacOSX "Snow Leopard" 10.6+ deadlock on sample-rate change submitted...

maccore: fixed MacOSX "Snow Leopard" 10.6+ deadlock on sample-rate change submitted by Olivier Tristan
and Stephane Letz with the following details:
"When using paMacCoreChangeDeviceParameters option of PaMacCore_SetupStreamInfo, if the sample rate used in PortAudio do not match the one on the hardware, it automatically switches the hardware samplerate. This functionality stopped working on 10.6 and was blocking the application when trying to change the hardware samplerate (infinite wait) It now works fine on 10.6 as it used to on previous OSX version."