gst/tcp/: Starting to prepare for specifying buffer time in other units than buffers. Expose remove reason in signal.

Original commit message from CVS:
* gst/tcp/gstmultifdsink.c: (gst_unit_type_get_type),
(gst_client_status_get_type), (gst_multifdsink_class_init),
(gst_multifdsink_init), (gst_multifdsink_remove_client_link),
(gst_multifdsink_handle_client_read),
(gst_multifdsink_handle_client_write),
(gst_multifdsink_recover_client), (gst_multifdsink_queue_buffer),
(gst_multifdsink_handle_clients), (gst_multifdsink_set_property),
(gst_multifdsink_get_property):
* gst/tcp/gstmultifdsink.h:
* gst/tcp/gsttcp-marshal.list:
Starting to prepare for specifying buffer time in other units
than buffers. Expose remove reason in signal.