MFC r316648:

Corrected misspelled versions of rendezvous.

The MFC maintains smp_no_rendevous_barrier() as a symbol alias of
smp_no_rendezvous_barrier().

__FreeBSD_version bumped to indicate presence of the new name
smp_no_rendezvous_barrier().

Reviewed by: gnn, jhb (email), kib
Differential Revision: https://reviews.freebsd.org/D10313