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Based on patch from Pavel Tvrdik

Also change linpool.current ptr to really point to thr current chunk.

Old code breaks with some versions of bison

ECMP is not enabled on BSD, where it is not supported by BIRD.

Several changes and bugfixes in Babel, namely:

- Exported route parameters stored directly in route table entry
- Exported non-babel routes no longer stored in per-entry route list
- Route update, selection and retraction simplified and fixed
- Route feasibility is evalualated per update and stored with route
- Unreachable route handling fixed, based on hold interval
- Added 'show babel routes' command

Overall, it fixes some issues with proper propagation of triggered
updates, making Babel convergence after topology change almost
instant.

Old behavior has several deficiencies compared to standard behavior
(no triggered updates for replies, no retransmissions, ...).

Babel TLV parsing code rejected IPv4 retractions without next-hop,
although next-hop is needed just for regular updates.

Also fix several minor bugs and add 'limit' option for k-out-of-j
link sensing strategy. Change default from 8-of-16 to 12-of-16.
Change IHU expiry factor from 1.5 to 3.5 (as in RFC 6126).