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

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