FreeBSD/src 33205c6 (r351188)sys/kern kern_synch.c, sys/sys refcount.h

Add a blocking wait bit to refcount.  This allows refs to be used as a simple
barrier.

Reviewed by:    markj, kib
Discussed with: jhb
Sponsored by:   Netflix
Differential Revision:  https://reviews.freebsd.org/D21254
DeltaFile
+70-0sys/kern/kern_synch.c
+45-25sys/sys/refcount.h
+115-252 files

UnifiedSplitRaw