Fix a few configure errors, pointed out by dougb@. Add new options. Add
v4l2 support (included in V4L option), though it may require 8.2 or later
to take full advantage of.
VAAPI option courtesy of Anonymous. 
Fix plist error discovered by pointyhat.
If you run this as SERVER_ONLY, you will need to manually disable V4L and
DVB if you do not wish to have this support. (Allows webcam live streams.)
PR: ports/153728 
Submitted by: Anonymous <email@example.com> 
Approved by: kwm (mentor)