[gimp] build/win: Upgrade libpng to 1.6.15

[Michael Henning <mhenning src gnome org>]

commit bb5effe95a09ba4ed2a503db1fb4dad8cf5dba65
Author: Michael Henning <drawoc darkrefraction com>
Date:   Thu Nov 27 12:16:13 2014 -0500

    build/win: Upgrade libpng to 1.6.15

 build/windows/jhbuild/imglibs.moduleset |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/build/windows/jhbuild/imglibs.moduleset b/build/windows/jhbuild/imglibs.moduleset
index f2c1f02..c685afb 100644
--- a/build/windows/jhbuild/imglibs.moduleset
+++ b/build/windows/jhbuild/imglibs.moduleset
@@ -21,9 +21,9 @@
 </autotools>
 
 <autotools id="libpng" autogen-sh="configure">
-       <branch version="1.6.12" repo="sf.net"
-                       module="libpng/libpng16/1.6.12/libpng-1.6.12.tar.xz"
-                       hash="sha1:c3d54f9ab683d63218361487269380fb8e0cf3b6">
+       <branch version="1.6.15" repo="sf.net"
+                       module="libpng/libpng16/1.6.15/libpng-1.6.15.tar.xz"
+                       hash="sha1:bddeac8ca97fbcf54d6d32c6eefed5d94b49df88">
        </branch>
        <dependencies>
                <dep package="zlib"/>