Support for ECMP on FreeBSD 13

[Zhenlei Huang]

Hi,

Currently Bird 2.x does not support ECMP on FreeBSD system.  Thanks Alexander V. Chernikov's work, 
the feature ECMP route was enabled by default in FreeBSD 13 amd64 GENERIC. Are there any plans Bird2.x 
will support ECMP on FreeBSD, or at least on FreeBSD 13 ?

Links:
https://gitlab.nic.cz/labs/bird/commit/f9f2e280ea4fa1af19d8ce9e54abeb495694c0d5?view=parallel
https://reviews.freebsd.org/D26449

Thanks,
zlei