Implement a way to announce flowspec rules without hitting Adj-RIB-In

Implement a way to announce flowspec rules without hitting Adj-RIB-In
and Loc-RIB. Flowspec objects are collected in a single flowrib RIB
and then directly distributed into the various Adj-RIB-Outs.
For this to work add a bypass in the filter logic (flowspec AFI/SAFI
are currently accepted without any rule). The filter language lacks
a way to allow prefixes based on AFI/SAFI which is the minimum needed.
OK tb@