Add BGRX and BGRA as supported video formats, since obs can handle them
directly. I unfortunately missed those when i initially wrote this
mapping due to my webcam not offering those formats.
Since the helper function also needs to pack/unpack the resolution, the
pack/unpack functions were moved to the helper library and prefixed with
v4l2_ in order to avoid possible collisions.
This moves some functions that are generic to a separate source
file. While doing so the api to those functions was improved to
be more generic and not depend on knowledge about the internal
structure of the plugin.
fryshorts