[DXVA] Fix h264 deconding with refs > 11 on recent Intel GPUs (SNB/IVB)

I found this set of patches at libav-devel mail lists. Here is discussion http://lists.libav.org/pipermail/libav-devel/2013-March/043945.html. 

This set of pathes fix using standartd Microsoft H.264 decoder (DXVA2_ModeH264_E) on Intel GPUs (SNB/IVB). Standard decoder works better with refs > 11. There are two sample video which played with artifacts when using old Intel h264 decoder (DXVADDI_Intel_ModeH264_E). 
https://cloclo11.datacloudmail.ru/weblink/get/7796485372b8/video/Gravity.h264.sample.mkv
https://cloclo11.datacloudmail.ru/weblink/get/7796485372b8/video/Startrek.h264.sample.mkv
With use standart decoder the artifacts are gone.

At the end of the discussion Luca Barbato says what it needs to be added to the list of improvements, but unfortunatly there is no upstream patch.

The lastest Intel drivers for IVB/Haswell has no support old Intel h264 decoder, so this actually for SandyBridge and older. 

ping @elupus

P.S. This patches are used into LAVFilters and MPC-HC player.