add back pngwrite read on all configs
add back pngwrite read on all configs

fireball-x/lwip,EyalAr/lwip,antoinepairet/lwip,domosapien/lwip,fireball-x/lwip,cocos-creator/lwip,fireball-x/lwip,EyalAr/lwip,weareu/lwip,domosapien/lwip,cocos-creator/lwip,mottx/lwip,EyalAr/lwip,EyalAr/lwip,mottx/lwip,mottx/lwip,domosapien/lwip,fireball-x/lwip,antoinepairet/lwip,antoinepairet/lwip,domosapien/lwip,weareu/lwip,cocos-creator/lwip,mottx/lwip,antoinepairet/lwip,weareu/lwip,weareu/lwip,cocos-creator/lwip