add libubox, a small utility library containing blob/blobmsg (structured...

add libubox, a small utility library containing blob/blobmsg (structured message format libraries), uloop, usock, list.h and the olsr avl tree implementation

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@25406 3c298f89-4303-0410-b956-a3cf2f4a3e73