move some 2.6.27 config stuff from ixp to generic, use slab instead of slub by...

move some 2.6.27 config stuff from ixp to generic, use slab instead of slub by default (slub crashes early on), enable kallsyms for now until the target is stable

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@12800 3c298f89-4303-0410-b956-a3cf2f4a3e73