pngtodo.txt - list of things to do for libpng

   allow user to #define out unused transformations
   medium memory model support
   overlaying one image on top of another
	optional palette creation
	histogram creation
	text conversion between different code types
   cHRM transformation
   support for other chunks being defined (sCAl, the gIF series,
      and others that people come up with).
	push reader
   pull writer
   better dithering
   keep up with public chunks
   other compression libraries
   more exotic interlace handling
   better filtering
   C++ wrapper
   other languages
   comments of > 64K

