[gtk-builder-win] Update libpng to version 1.6.12

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 2168fcce8f03afa57a544bd6032ffa6cc083270d
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Fri Jun 27 09:51:49 2014 +0200

    Update libpng to version 1.6.12

 win32/libs/31_libpng.bat |    4 ++--
 win64/libs/31_libpng.bat |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/win32/libs/31_libpng.bat b/win32/libs/31_libpng.bat
index 67c041b..19c7e8e 100644
--- a/win32/libs/31_libpng.bat
+++ b/win32/libs/31_libpng.bat
@@ -1,8 +1,8 @@
-MODVER=1.5.14
+MODVER=1.6.12
 
 mkdir -p 31_libpng
 cd 31_libpng
-test -f libpng-$MODVER.tar.xz || wget 
http://sourceforge.net/projects/libpng/files/libpng15/older-releases/$MODVER/libpng-$MODVER.tar.xz
+test -f libpng-$MODVER.tar.xz || wget 
http://sourceforge.net/projects/libpng/files/libpng16/$MODVER/libpng-$MODVER.tar.xz
 xz -d -k -f libpng-$MODVER.tar.xz
 tar -xf libpng-$MODVER.tar
 cd libpng-$MODVER
diff --git a/win64/libs/31_libpng.bat b/win64/libs/31_libpng.bat
index 34e88ad..d2ac340 100644
--- a/win64/libs/31_libpng.bat
+++ b/win64/libs/31_libpng.bat
@@ -1,8 +1,8 @@
-MODVER=1.5.14
+MODVER=1.6.12
 
 mkdir -p 31_libpng
 cd 31_libpng
-test -f libpng-$MODVER.tar.xz || wget 
http://sourceforge.net/projects/libpng/files/libpng15/older-releases/$MODVER/libpng-$MODVER.tar.xz
+test -f libpng-$MODVER.tar.xz || wget 
http://sourceforge.net/projects/libpng/files/libpng16/$MODVER/libpng-$MODVER.tar.xz
 xz -d -k -f libpng-$MODVER.tar.xz
 tar -xf libpng-$MODVER.tar
 cd libpng-$MODVER