ecsv --- Use libpng to do load images as full (A)RGB images
The pngrw functionality for loading PNG files failed to load many texture
images because it didn't expect the bit depth and similar parameters. Rice only
needs 24/32 bit png files and therefore it is good enough to use the libpng
functionality to load all files as (A)RGB images.

Ported change over from Rice Vidoe linux, change is by ecsv https://bitbucket.org/ecsv