Log Message:
Changes 1.0.8:

bugfixes:
* fixed problem with PAST usage where source > dest

core:
* added missing get-/put-chunk-jdaa
* added CRC existence & checking flags
* added data-push mechanisms for specialized decoders
* some speed optimizations (thanks to John Stiles)
* defend against using undefined closestream function
* defend against using undefined openstream function
* added check for extreme chunk-lengths
* change worst-case iAlphadepth to 1 for standalone PNGs
* added support for 3+byte pixelsize for JPEG's
* added conditional to allow easier writing of large MNG's