Updates FMJ to r28 which implements shrinking of the audio RTP packet queue/jitter buffer.

Conflicts:
	lib/fmj.jar
Employs packet loss concealment (PLC) for the Opus and SILK audio codecs.

Conflicts:
	src/org/jitsi/impl/neomedia/codec/audio/silk/JavaDecoder.java
Fixes recent breakage of FEC decoding in the Opus codec.