Added extra field to STATE_CHANGE message with the pending state, which will be different from the new state soon.

Original commit message from CVS:
* check/gst/gstbin.c: (GST_START_TEST):
* check/gst/gstmessage.c: (GST_START_TEST):
* check/gst/gstpipeline.c: (GST_START_TEST), (message_received):
* gst/gstelement.c: (gst_element_commit_state),
(gst_element_lost_state):
* gst/gstmessage.c: (gst_message_new_state_changed),
(gst_message_parse_state_changed):
* gst/gstmessage.h:
* tools/gst-launch.c: (event_loop):
Added extra field to STATE_CHANGE message with the pending
state, which will be different from the new state soon.