This change introduces loadable route lookup modules based on DPDK rte_lpm lib targeted for high-speed lookups in large-scale tables.
It is based on the lookup framework described in D27401.
IPv4 module is called **dpdk_lpm4**. It wraps around [rte_lpm](https://doc.dpdk.org/guides/prog_guide/lpm_lib.html), which implement variation of [DIR24-8](http://yuba.stanford.edu/~nickm/papers/Infocom98_lookup.pdf) lookup algorithm. Module provide lockless route lookups and in-place incremental updates, allowing for good RIB performance.
IPv6 module is called **dpdk_lpm6**. It wraps around [rte_lpm6](https://doc.dpdk.org/guides/prog_guide/lpm6_lib.html).
Implementation can be seen //as multi-bit trie where the stride or number of bits inspected on each level varies from level to level.//... //It can vary from 1 to 14 memory accesses, with 5 being the average value for the lengths that are most commonly used in IPv6.//. Module provide lockless route lookups **for global unicast addresses** and in-place incremental updates, allowing for good RIB performance.
* wrapper code lives in `sys/contrib/dpdk_rte_lpm/dpdk_lpm.c`.
* rte_lpm implementation contains both RIB ("rule_" code, backed by array of hash tables) and fib code. RIB code part has been commented out, as base radix already provides all the necessary primitives.
* link-local lookups are currently implemented as base radix lookup. This part should be converted to something like read-only radix trie.