Patch by Alfredo de Greef with high quality image texture filters. This adds 3 new filters: * SAT: Summed Area Tables. This is like mipmaps, but using somewhat more memory avoids some artifacts. * EWA: Ellipitical Weighted Average, anisotropic filter. * FELINE: Fast elliptical lines for anisotropic texture mapping. The one change I made to this was to try to fix an alpha/premul problem, hopefully I didn't break anything, it looks compatible with the existing filter now for me.