Video4Linux2 sup­port in FreeBSD (linuxu­lat­or)

I com­mit­ted the v4l2 sup­port in­to the lin­ux­u­la­tor (in 9–cur­rent). Part of this was the im­port of the v4l2 head­er from linux. We have the per­mis­sion to use it (like the v4l one), it is not li­censed via GPL. This means we can use it in FreeBSD nat­ive dri­vers, and they are even al­lowed to be com­piled in­to GENERIC (but I doubt we have a dri­ver which could pro­vide the v4l2 inter­face in GENERIC).

The code I com­mit­ted is “just” the glue-​code which al­lows to use FreeBSD nat­ive devices which pro­vide a v4l2 inter­face (e.g. multimedia/​pwcbsd or multimedia/​webcamd) from linux pro­grams.

Thanks to nox@ for writ­ing the glue code.