Modules TSC: Add mutex for server.lruclock.

Only useful for when no atomic builtins are available.

src/server.h

@@ -861,6 +861,7 @@ struct redisServer {
     dict *orig_commands;        /* Command table before command renaming. */
     aeEventLoop *el;
     unsigned int lruclock;      /* Clock for LRU eviction */
+    pthread_mutex_t lruclock_mutex;
     int shutdown_asap;          /* SHUTDOWN needed ASAP */
     int activerehashing;        /* Incremental rehash in serverCron() */
     int active_defrag_running;  /* Active defragmentation running (holds current scan aggressiveness) */