seamonkey: fixed build by setting default toolkit to 'cairo-gtk2' and by not using systems libpng

www/seamonkey/seamonkey.conf

@@ -2,7 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../seamonkey/seamonkey.conf
-# Copyright (C) 2007 The OpenSDE Project
+# Copyright (C) 2007 - 2010 The OpenSDE Project
 # Copyright (C) 2004 - 2006 The T2 SDE Project
 # Copyright (C) 1998 - 2004 Clifford Wolf
 #
@@ -27,6 +27,8 @@ ac_add_options --enable-extensions=default,venkman,inspector
 ac_add_options --enable-jsd
 ac_add_options --enable-mathml
 ac_add_options --enable-module=psm
+ac_add_options --enable-default-toolkit=cairo-gtk2
+ac_add_options --without-system-png
 EOT
 }