stream: don't include linux/types.h in some files

Apparently this is not portable to FreeBSD. It turns out that we
(probably) don't use any symbols defined by this header directly, so
the includes are not needed.
tvi_v4l2: let libv4l2 convert to a known pixel format

Signed-off-by: wm4 <wm4@nowhere>

Significant modifications over the original patch by not overriding
syscalls with macros ("#define open v4l2open") for fallback, but the
other way around ("#define v4l2open open"). As consequence, the calls
have to be replaced throughout the file.

Untested, although the original patch probably was tested.
configure: enable v4l2 input on freebsd
tvi_v4l2: remove VBI stuff

This used to be needed for teletext support. Teletext commit has been
removed (see commit ebaaa41f), and it appears this code is inactive.
It was just forgotten with the removal. Get rid of it completely.

Untested. (Like all changes to the TV code.)