daemon: enable H263 encoder

H263 version 1 allows a limited range of resolutions outdated compared
to recent camera capabilities. It was thus nearly impossible
to use it on Ring.

This patchset forces encoding of H263+ which supports all resolutions
multiple of 4 from 4x4 to 2048x1152.
On Libav we see video artifacts if multithread is enabled
on encoder side. A workaround deals with forcing h263 encoder
to monothread.

See https://bugzilla.libav.org/show_bug.cgi?id=912

Tuleap: #138
Change-Id: I7121e182fa13139d28db010e2ed0de573c616de7