Added lodepng.c (renamed from lodepng.cpp), lodepng.h and LICENSE from
the LodePNG project by Lode Vandevenne.
https://github.com/lvandeve/lodepng
Since this code is licensed separately from the cabi code, it has been
placed in its own subdirectory named lodepng.
cabi.c and README.md have been modified for the LodePNG file location.
Scott Allen