My mkvmerge version seems to generate broken files.

 * use /dev/fb0 as default (like suggested in the help string)
 * fix a typo (intf_sys_t != intf_thread_t)
 * cleanings.

Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

Nominated for the price of the ugliest commitdiff

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

It only works for blend and X mode but there are probably the most used.
When blend/X are enabled/disabled:
 - It avoids recreating the vout.
 - It avoids deinterlacing the (soft) subtitles.
The other modes are not possible without a lot of vout works, so it is
postponed for later.

As a side effect, the initial value of the menu now takes into account the
command line options.

Please, report any regression. This code is made complicated by the
vout filter/video filter2 switches&tricks.

The current code assume it everywhere.

It now supports I422 and discard mode.