Bilinear downscale tweaks plus bicubic
No half-pixel fix needed for bicubic
Use half-pixel for all bilinear downscales, tune int/float conversions
Actually write bicubic rows
Fix rounding for bicubic, data types and performance tuning
Better large downscales, sanity checks, fix dimension rounding
Merge pull request #18 from Lithopsian/rc1

Bilinear downscale tweaks, bicubic, data types.  Sanity check needed?