New branch filter_cl.
New branch filter_cl.

This branch will add new kernels for all of the subpixel and bilinear filter
modes. Essentially ALL of the public filter_c.c functions will become kernels
with the private functions becoming CL helpers.

Once that is done, then I try to expand all of the rest of the reconintra/reconinter functions
into kernels.

awatry/libvpx.opencl,awatry/libvpx.opencl,awatry/libvpx.opencl,awatry/libvpx.opencl