Contrib: update libpng to 1.2.43

Yes, I know, I am not using 1.4.1...

extras/contrib/src/packages.mak

@@ -139,7 +139,7 @@ VCDIMAGER_VERSION=0.7.23
 VCDIMAGER_URL=$(GNU)/vcdimager/vcdimager-$(VCDIMAGER_VERSION).tar.gz
 CDIO_VERSION=0.80
 CDIO_URL=$(GNU)/libcdio/libcdio-$(CDIO_VERSION).tar.gz
-PNG_VERSION=1.2.42
+PNG_VERSION=1.2.43
 PNG_URL=$(SF)/libpng/libpng-$(PNG_VERSION).tar.bz2
 GPGERROR_VERSION=1.7
 #GPGERROR_URL=$(CONTRIB_VIDEOLAN)/libgpg-error-$(GPGERROR_VERSION).tar.bz2