gst/base/gstbasesink.c: Some more debugging.

gst/base/gstbasesink.c: Some more debugging.

Original commit message from CVS:
* gst/base/gstbasesink.c: (gst_base_sink_handle_object),
(gst_base_sink_do_sync), (gst_base_sink_get_position):
Some more debugging.

* gst/base/gstbasetransform.c: (gst_base_transform_finalize),
(gst_base_transform_init), (gst_base_transform_buffer_alloc),
(gst_base_transform_event), (gst_base_transform_getrange),
(gst_base_transform_chain):
* gst/base/gstbasetransform.h:
Fix debugging,
Protect transform and concurrent buffer alloc with a new lock.
Try not to break ABI/API.