uClibc:
 * add support for libubacktrace required for uClibc-0.9.33.x based firmwares
 * menuconfig-tested only
 * refs #2103, refs #1939


git-svn-id: file:///var/svn/freetz/trunk@10528 149334a1-2f27-0410-a3b9-fc62619ac1e6