disable the MSS fixup hack by default (most ISPs don't require this as a...

disable the MSS fixup hack by default (most ISPs don't require this as a workaround for MTU problems, only some do). this should give a nice speedup for routing on standard-compliant ISPs

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@13788 3c298f89-4303-0410-b956-a3cf2f4a3e73