gst/elements/: Added datarate properties to limit the datarate.

gst/elements/: Added datarate properties to limit the datarate.

Original commit message from CVS:
* gst/elements/gstfakesrc.c: (gst_fakesrc_class_init),
(gst_fakesrc_init), (gst_fakesrc_set_clock),
(gst_fakesrc_set_property), (gst_fakesrc_get_property),
(gst_fakesrc_get), (gst_fakesrc_change_state):
* gst/elements/gstfakesrc.h:
* gst/elements/gstidentity.c: (gst_identity_class_init),
(gst_identity_init), (gst_identity_chain),
(gst_identity_set_property), (gst_identity_get_property),
(gst_identity_change_state):
* gst/elements/gstidentity.h:
Added datarate properties to limit the datarate.