main/libpng: upgrade to 1.4.0

main/libpng/APKBUILD

 # Contributor: Carlo Landmeter <clandmeter at gmail>
 # Maintainer: Carlo Landmeter <clandmeter at gmail>
 pkgname=libpng
-pkgver=1.2.40
+pkgver=1.4.0
 pkgrel=0
 pkgdesc="Portable Network Graphics library"
 url="http://www.libpng.org/"
@@ -27,4 +27,4 @@ package() {
 	install -Dm644 LICENSE "${pkgdir}"/usr/share/licenses/${pkgname}/LICENSE || return 1
 }
 
-md5sums="a2f6808735bf404967f81519a967fb2a  libpng-1.2.40.tar.gz"
+md5sums="dfa01122db3be9808a8c9ace7d0580fd  libpng-1.4.0.tar.gz"