rtpproto: Support IGMPv3 source specific multicast inclusion

Blocking/exclusion is not supported yet.

The rtp protocol parameter takes the same form as the existing
sources parameter for the udp protocol.

Signed-off-by: Martin Storsjö <martin@martin.st>
rtpproto: Check the source IP if one single source has been specified

If another peer is sending unicast packets to the same port that
we are listening on, those packets can end up being received despite
using source specific multicast. For those cases, manually check the
source address of received packets against the intended source address.

This only handles the case when the source list is one single IP
address for now, which probably is the most common case.

Based on a patch by Ed Torbett.

Signed-off-by: Martin Storsjö <martin@martin.st>
rtsp: Support multicast source filters (RFC 4570)

This supports inclusion of one single IP address for now,
at the media level. Specifying the filter at the session level
(instead of at the media level), multiple source addresses,
exclusion, or using FQDNs instead of plain IP addresses is not
supported (yet at least).

Signed-off-by: Martin Storsjö <martin@martin.st>