More ETC1 cluster fit data

Ignore the SSIM stats, this is a corpus test image with random 4x4 blocks chosen from many other images.

This was on a 20 core Xeon workstation, with multithreading enabled in basislib and etc2comp (40 threads each). The API I'm using in etcpak is not threaded (it's already sorta ridiculously fast), and Intel is not multithreaded either. (As far as I can tell from breakpointing inside it.) etcpak and Intel make heavy use of SIMD operations, while etc2comp and basislib do not.

Cluster fit (new algorithm):

J:\dev\basislib1\bin>texexp test_0.tga
perceptual: 0 etc2: 0 rec709: 1
Source filename: test_0.tga 4096x4096
--- basislib Quality: 4
basislib pack time: 4.211
basislib ETC image Error: Max: 255, Mean: 3.277, MSE: 40.847, RMSE: 6.391, PSNR: 32.019, SSIM: 0.999618

--- etc2comp effort: 100
etc2comp time: 154.562167
etc2comp Error: Max: 255, Mean: 3.286, MSE: 42.777, RMSE: 6.540, PSNR: 31.819, SSIM: 0.999612

--- etcpak time: 0.258
etcpak Error: Max: 255, Mean: 4.282, MSE: 69.927, RMSE: 8.362, PSNR: 29.684, SSIM: 0.998407

--- ispc_etc time: 43.694160
ispc_etc1 Error: Max: 255, Mean: 3.249, MSE: 39.912, RMSE: 6.318, PSNR: 32.120, SSIM: 0.999655

Previous algorithm (rg_etc1's lattice scan+refinement):

J:\dev\basislib1\bin>texexp test_0.tga
perceptual: 0 etc2: 0 rec709: 1
Source filename: test_0.tga 4096x4096

--- basislib Quality: 4
basislib pack time: 240.638
basislib ETC image Error: Max: 255, Mean: 3.203, MSE: 39.336, RMSE: 6.272, PSNR: 32.183, SSIM: 0.999680

--- etc2comp effort: 100
etc2comp time: 151.739932
etc2comp Error: Max: 255, Mean: 3.286, MSE: 42.777, RMSE: 6.540, PSNR: 31.819, SSIM: 0.999612

--- etcpak time: 0.243
etcpak Error: Max: 255, Mean: 4.282, MSE: 69.927, RMSE: 8.362, PSNR: 29.684, SSIM: 0.998407

--- ispc_etc time: 46.807596
ispc_etc1 Error: Max: 255, Mean: 3.249, MSE: 39.912, RMSE: 6.318, PSNR: 32.120, SSIM: 0.999655