bird: Update to version 2.0.8

bird: Update to version 2.0.8

- Update from 2.0.7 to 2.0.8
- Update of rootfile not required
- Changelog
   Version 2.0.8 (2021-03-18)
     o Automatic channel reloads based on RPKI changes
     o Multiple static routes with the same network
     o Use bitmaps to keep track of exported routes
     o Per-channel debug flags
     o CLI commands show info from multiple protocols
     o Linux: IPv4 routes with IPv6 nexthops
     o Filter: Optimized redesign of prefix sets
     o Filter: Improved type checking of user filters
     o Filter: New src/dst accessors for Flowspec and SADR
     o Filter: New 'weight' route attribute
     o Filter: BGP path mask loop operator
     o Filter: Remove quitbird command
     o RIP: Demand circuit support (RFC 2091)
     o BGP: New 'allow as sets' and 'enforce first as' options
     o BGP: Support for BGP hostname capability
     o BGP: Support for MD5SIG with dynamic BGP
     o BFD: Optional separation of IPv4 / IPv6 BFD instances
     o BFD: Per-peer session options
     o RPKI: Allow build without libSSH
     o RPKI: New 'ignore max length' option
     o OSPF: Redesign of handling of unnumbered PtPs
     o OSPF: Allow key id 0 in authentication
     o Babel: Use onlink flag for routes with unreachable next hop
     o Many bugfixes
   Notes:
     Automatic channel reloads based on RPKI changes are enabled by default,
      but require import table enabled when used in BGP import filter.
     BIRD now uses bitmaps to keep track of exported routes instead of
      re-evaluation of export filters. That should improve speed and accuracy in
      route export handling during reconfiguration, but takes some more memory.
     Per-channel debug logging and some CLI commands (like 'show ospf neighbors')
      defaulting to all protocol instances lead to some minor changes in log and
      CLI output. Caution is recommended when logs or CLI output are monitored by
      scripts.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>