Fix deadlock when closing video devices / setting producers

Ignore-this: 5d38264b321defad22ab7c10eee51669

darcs-hash:20141014143609-56b4d-2103528ec4fa697c2bb458263b65bd19e90ace01
Properly close video devices on __dealloc__

Ignore-this: 1cbe532fb3516eec97e7f16ed9fb789e

darcs-hash:20141014143617-56b4d-ea6eea055161fea65746a323647a0fb557a33994
Close video producer when SIPApplication ends

Ignore-this: 5518f8cce5a8053e0e5bf3cbd0d03806

darcs-hash:20141014143629-56b4d-9eff2efb019cadbd4c378180abd04499a988eaff
pjsip: fix compilation with libav

Ignore-this: c71bf88d25177c29042845ee0b5c00d7

darcs-hash:20141015151743-56b4d-0deb42cb4e8be724d1af207f7ffbc0c9533c1054