was using wrong header

kern/synchprobs/traffic_synch.c

@@ -2,7 +2,7 @@
 #include <lib.h>
 #include <synchprobs.h>
 #include <synch.h>
-#include <thread.h>
+#include <wchan.h>
 #include <opt-A1.h>
 
 /*