lodepng update

[Lutger]

Lodepng has been updated. Lodepng is a smallish png codec with minimal 
dependencies, originally written in C++ by Lode Vandevenne.

You can get lodepng via dsss net install, or use these links:

http://lutger.ifastnet.com/lodepng/lpng07082007.zip //source
http://lutger.ifastnet.com/lodepng/lpngdoc.zip // docs
http://lutger.ifastnet.com/lodepng/lodepng.Decode.html //online docs

Main changes since last version:
- works with Tango (you need phobos' binding to zlib)
- refactored to better fit the D programming language
- changed and extended api (still simple and procedural)
- the decoder is compliant to the png spec and the encoder works 
properly (tested with the png suite)
- (better) support for transparency, background color, textual metadata
- various bugfixes