gst/tcp/gstmultifdsink.*: More multifdsink stats. Avoid deadlock by releasing locks before sending out a signal.

Original commit message from CVS:
* gst/tcp/gstmultifdsink.c: (gst_multifdsink_class_init),
(gst_multifdsink_add), (gst_multifdsink_get_stats),
(gst_multifdsink_client_remove),
(gst_multifdsink_handle_client_write),
(gst_multifdsink_queue_buffer):
* gst/tcp/gstmultifdsink.h:
More multifdsink stats. Avoid deadlock by releasing locks
before sending out a signal.