SCTP-disabled in RTCMultiConnection-v1.4 and DataChannel.js

Chrome doesn't support message fragmentation i.e. chunking; also max
limit is 100k; however I used 40k. That's why it failed.

Chunk size should be 16k to meet Firefox's needs!

RTCMultiConnection features onmute/onunmute fails on Firefox because
"Firefox" doesn't set "label" and "id" attributes to "LocalMediaStream"
object. It will be fixed in next v1.4 updates.