Contribs: add png

Remove the old way with using the static makefiles and weird ??PREFIX?? patches

contrib/src/png/SHA512SUMS

+f1dc2afd747554e5fda1c7627e34530d845d8c7f5629870a21f0d501604cba26446aa7a7bbeb8278f3ab714ed48cf2518df873d0e8fee4dc79d5e2b50060ce46  libpng-1.4.7.tar.bz2

contrib/src/png/rules.mak

+# PNG
+PNG_VERSION := 1.4.7
+PNG_URL := $(SF)/libpng/libpng-$(PNG_VERSION).tar.bz2
+
+PKGS += png
+
+$(TARBALLS)/libpng-$(PNG_VERSION).tar.bz2:
+	$(call download,$(PNG_URL))
+
+.sum-png: libpng-$(PNG_VERSION).tar.bz2
+
+png: libpng-$(PNG_VERSION).tar.bz2 .sum-png
+	$(UNPACK)
+	$(MOVE)
+
+.png: png
+	$(RECONF)
+	cd $< && $(HOSTVARS) ./configure $(HOSTCONF)
+	cd $< && $(MAKE) install
+	touch $@