mac: Fix incorrect device list after device removal

On Mac OS X 10.8.x (Mountain Lion), if a device is connected, opened, then
closed, then unplugged, subsequent calls to hid_enumerate() will still
list the device (even though it's been unplugged).  If the device is
plugged in again, a second instance will show up in the list and often it
will be impossible to open either.  Github user TamToucan figured out that
in hid_enumerate() if a call is made to IOHIDManagerSetDeviceMatching()
before the call to IOHIDManagerCopyDevices() that this will clear the
problem.

Thanks to TamToucan for figuring this out.

Author: signal11

mac/hid.c

@@ -420,6 +420,7 @@ struct hid_device_info  HID_API_EXPORT *hid_enumerate(unsigned short vendor_id,
 	process_pending_events();
 
 	/* Get a list of the Devices */
+	IOHIDManagerSetDeviceMatching(hid_mgr, NULL);
 	CFSetRef device_set = IOHIDManagerCopyDevices(hid_mgr);
 
 	/* Convert the list into a C array so we can iterate easily. */