contrib/mnit: intro the libpng base code for the Android platform

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
contrib/mnit: configure the png library for android

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
contrib/mnit: add Android specific makefiles to the png library

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
contrib/mnit: fix reference to the png library

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>