Series-based resizing would be faster if implemented directly
Handle fixed-point overflow in GM fixed
Small memory leak in giflib
BMP RLE support
BMP OS/2 format support
Some older versions of giflib don't have DGifGetExtensionNext, require minimum version
Transparent SBS icons get a transparent background with gd_fixed for some reason
Remove GM code, the filters are wrong and it's not faster anyway
Display the filename even if passing in raw data (embedded images)

Tests:
  Corrupt/invalid files in all formats, triggering longjmp's
  PNG <8-bit gray
  JPEG invalid marker, should continue (Michael's image)
