Adds some OpenMAX 1.1.2 IL extension headers.

Includes index and video extension headers
in order to support vpx specific parameters
and enable vpx encoder.

Note that existing (seemingly modified) version
of OMX_Video.h semantically conflicts with
official OMX_VideoExt.h because former includes
OMX_Video_CodingVPX as OMX_VIDEO_CODINGTYPE
whereas official extension headers denote
it as OMX_VIDEO_CodingVP8 within
OMX_VIDEO_CODINGEXTTYPE.

Change-Id: Ibab9663fcbc9c406a2cfb4bf79fe21e3b01a6e66
Signed-off-by: Kunter Gultekin <kuntergultekin@google.com>