Update videodev2.h to the version from linux kernel 2.6.34.14.
This version is dual-licensed: 3 clause BSD license and GPL v2+.
- Move videodev headers from compat/linux to contrib/v4l (cp from vendor and
  apply diff to compat/linux versions).
- The cp implies an update of videodev2.h to the linux kernel 2.6.34.14 one.

The update makes video in skype v4 work on FreeBSD.

Tested by:	Artyom Mirgorodskiy <artyom.mirgorodsky@gmail.com>
		(update of header only)
Add SDT_PROBE_DEFINE0 for consistency with SDT_PROBE0.

MFC after:	1 week
Add a man page for the SDT_* macros, which can be used to define new static
DTrace probes and providers in kernel code.

MFC after:	1 week