Moved hash state to acolorhash_table
Moved edge/noise bitmaps to image struct
Image mem cleanup
Modified image flag
Moved libpng critical section down
Exposed hash alloc/free methods
acolorhash_table holds maxcolors and ignorebits
Explicit palette generation/remapping steps
Output image mem cleanup
Moved hist hash table out of pam
Moved palette sorting to quantization step
Changed internal gamma to 0.55
LUT for gamma
Moved creation of row_pointers to rwpng