gimp security update

2:2.6.9-6 - fix overflow in XWD loader CVE-2013-1913, CVE-2013-1978 2:2.6.9-5 - fix overflow in XWD loader 879302 2:2.6.9-5 - fix overflow in GIF loader 847303 2:2.6.9-5 - fix overflows in GIF, CEL loaders 727800, 839020 2:2.6.9-4.1 - fix various overflows 666793, 703403, 703405, 703407, 704512...