mpegtsmux: Add support for muxing SI tables

mpegtsmux: Add support for muxing SI tables

The muxer is now able to include DVB sections in the transport stream.

The si-interval property will determine how often the SI tables are
muxed into the stream.

The section is handled by the mpeg-ts library. Below is a small example
that will include a Netork Information Table with a Network Name
descriptor in the stream.

GstMpegTsNIT *nit;
GstMpegTsDescriptor *descriptor;
GstMpegTsSection *section;
GstElement *mpegtsmux;

gst_mpegts_initialize ();

nit = gst_mpegts_section_nit_new ();
nit->actual_network = TRUE;

descriptor = gst_mpegts_descriptor_from_dvb_network_name ("Network name");
g_ptr_array_add (nit->descriptors, descriptor);

section = gst_mpegts_section_from_nit (nit);

// mpegtsmux should be retrieved from the pipeline
gst_mpegts_section_send_event (section, mpegtsmux);
gst_mpegts_section_unref (section);