Merging-in the OpenCL Scaling code from the OpenCL branch to trunk. 
Patch originally by the Multicoreware Inc team, followed by improvements and fixes by Micheal Wootton from AMD Inc,

OpenCL:
This patch implements Bicubic Scaling in OpenCL.  
Note that HandBrake currently uses Lanczos so the performance difference appears to be much more significant. We may offer an option of BiCubic in software later.
Bicubic scaling may appear a bit sharper than the equivalent Lanczos encode and may increase file size a bit. Quality may be better or worse depending on the scaling and content and personal preference towards sharpness.
When comparing performance with a custom HandBrake build that runs Software Bicubic to OpenCL Bicubic, performance increase is about 5~7% on average on a modern GPU.


Hardware Decode via DXVA:
We also have optional DXVA decoding which may come in useful for slower/lower end systems that have a capable GPU.
This is only available on input sources that use the libav decode path.
Most GPU hardware for decoding is designed for playback, so if you are running on a high end CPU, it will bottleneck the encode process.

Requires OpenCL 1.1 or later supporting GPU.

Front end changes and testing framework are not included in this patch. This will be resolved later.

Patch will be revised further before the UI is implemented.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5792 b64f7644-9d1e-0410-96f1-a4d463321fa5
Tidyup a warning in oclscale.c

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5793 b64f7644-9d1e-0410-96f1-a4d463321fa5