x86: AVX2 deblock strength

30->18 cycles
x86: AVX2 high bit-depth intra_sad_x3_8x8

43->24 cycles
x86: AVX2 intra_sad_x3_8x8c

30->22 cycles
x86: faster AVX2 quant_4x4x4

10->9 cycles
x86: AVX2 add16x16_idct_dc

27 -> 19 cycles
x86: AVX2 high bit-depth quant

quant_4x4: 13->6 cycles
quant_4x4_dc: 14->8 cycles
quant_8x8: 47->24 cycles
quant_4x4x4: 48->25 cycles
x86: AVX2 high bit-depth denoise_dct

28->15 cycles

Also reorder instructions to use fewer registers, 3 cycles faster on Ivy Bridge with 64-bit Windows.
x86-64: 64-bit variant of AVX2 hpel_filter

~5% faster than 32-bit.
x86: AVX2 high bit-depth dequant
x86: AVX2 dequant_4x4_dc
OpenCL support refactoring

Autoload the OpenCL library so that it's not required to run an openCL-enabled
build of x264.

Update X264_BUILD, which should have been changed with the first patch.