gst/gdp/gstgdpdepay.c: Disable seeking.

gst/gdp/gstgdpdepay.c: Disable seeking.

Original commit message from CVS:
* gst/gdp/gstgdpdepay.c: (gst_gdp_depay_init),
(gst_gdp_depay_finalize), (gst_gdp_depay_sink_event),
(gst_gdp_depay_src_event), (gst_gdp_depay_chain),
(gst_gdp_depay_change_state):
Disable seeking.
Small cleanups.
Clear adapter on disconts.
Clear caps when going to READY instead of NULL
* gst/gdp/gstgdppay.c: (gst_gdp_pay_class_init),
(gst_gdp_pay_init), (gst_gdp_pay_finalize), (gst_gdp_pay_reset),
(gst_gdp_buffer_from_caps), (gst_gdp_pay_buffer_from_buffer),
(gst_gdp_buffer_from_event), (gst_gdp_pay_reset_streamheader),
(gst_gdp_queue_buffer), (gst_gdp_pay_chain),
(gst_gdp_pay_sink_event), (gst_gdp_pay_src_event),
(gst_gdp_pay_change_state):
* gst/gdp/gstgdppay.h:
Reset payloader when going to READY.
Fix leaked buffers in ->queue on push errors.
Disable seeking.
Code cleanups.
Create packetizer in _init, free in _finalize.