gdp: add a GstDPPacketizer object, and create/free functions

gdp: add a GstDPPacketizer object, and create/free functions

Original commit message from CVS:
* libs/gst/dataprotocol/dataprotocol.c:
(gst_dp_header_from_buffer_any), (gst_dp_packet_from_caps_any),
(gst_dp_version_get_type), (gst_dp_init),
(gst_dp_header_from_buffer), (gst_dp_header_from_buffer_1_0),
(gst_dp_packet_from_caps), (gst_dp_packet_from_caps_1_0),
(gst_dp_packet_from_event), (gst_dp_packet_from_event_1_0),
(gst_dp_event_from_packet_0_2), (gst_dp_event_from_packet_1_0),
(gst_dp_event_from_packet), (gst_dp_packetizer_new),
(gst_dp_packetizer_free):
* libs/gst/dataprotocol/dataprotocol.h:
API: add a GstDPPacketizer object, and create/free functions
API: add GstDPVersion enum
Add 1.0 event function that uses the string serialization
Serialize more useful buffer flags
Fixes #343988