fix call mute-state for multiple calls

added audio_ismuted() and remove static state from menu.c

thanks to Remik who reported the issue and suggested
a nice solution :)
call: cancel local timer on call_progress()

for incoming calls, we start a local timer of 120 seconds.
this timer is stopped when the call is answered with
200 or 183.

issue was reported by Victor Sergienko, thanks!
move struct stream to core.h
Merge remote-tracking branch 'upstream/master'
Move XRTP stats to audio and implement EN/DE parameters