Add advertising address support

- New command line option: -A addr
- Can work in bridging mode as well: -A addr1/addr2
- Bridging mode has to be used when rtpproxy is started in bridging mode

Updated original patch from https://github.com/miconda/rtpproxy/commit/41f6d9d9084a6fad52a6483a0593d4b25e0de8ca