main/libpng: upgrade to 1.2.38

main/libpng/APKBUILD

 # Contributor: Carlo Landmeter <clandmeter at gmail>
 # Maintainer: Carlo Landmeter <clandmeter at gmail>
 pkgname=libpng
-pkgver=1.2.37
+pkgver=1.2.38
 pkgrel=0
 pkgdesc="Portable Network Graphics library"
 url="http://www.libpng.org/"
@@ -24,4 +24,4 @@ build() {
 	install -Dm644 LICENSE "${pkgdir}"/usr/share/licenses/${pkgname}/LICENSE || return 1
 }
 
-md5sums="7480dbbf9f6c3297faf6fe52ec9b91ab  libpng-1.2.37.tar.gz"
+md5sums="99900634a47041607a031aa597d51e65  libpng-1.2.38.tar.gz"