URL: http://www.libpng.org/pub/png/libpng.html
Version: 1.6.22rc01
License: libpng license
License File: LICENSE, pulled out of png.h
Description: png compression/decompression library
Local Modifications:
    (1) Created pnglibconf.h from pnglibconf.h.prebuilt. This
    is mostly a rename, with Skia-specific settings at the end.
    The only difference is for pngprefix.h.
    (2) Included Intel optimizations by running:
    "patch -i contrib/intel/intel_sse.patch -p1"
    (3) Removed files unused by Skia
    (4) Fixed an undefined behavior bug (skbug.com/5390)
    (5) Add pngprefix.h, so multiple versions of libpng can
    coexist.