Merge pull request #4497 from opensourcerouting/rcu

RCU support

diff --cc lib/log.c
Simple merge

diff --cc lib/subdir.am
Simple merge

diff --cc lib/thread.c
index f862ce5eb0697ac2f44bd2019ddd879bc6c6c9ff,0436f31c3de6615d9be7af7e090ea6c08132949e..5756ebc1f99920b0eaaa02fab8ad48689e8b303c
--- 1/lib/thread.c
--- 2/lib/thread.c
+++ b/lib/thread.c
@@@ -25,8 -25,10 +25,9 @@@
  
  #include "thread.h"
  #include "memory.h"
+ #include "frrcu.h"
  #include "log.h"
  #include "hash.h"
 -#include "pqueue.h"
  #include "command.h"
  #include "sigevent.h"
  #include "network.h"