rib: add RIB library

rib: add RIB library

Add RIB (Routing Information Base) library. This library
implements an IPv4 routing table optimized for control plane
operations. It implements a control plane struct containing routes
in a tree and provides fast add/del operations for routes.
Also it allows to perform fast subtree traversals
(i.e. retrieve existing subroutes for a given prefix).
This structure will be used as a control plane helper structure
for FIB implementation. Also it might be used standalone in other
different places such as bitmaps for example.
Internal implementation is level compressed binary trie.

Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>