BUILD: threads: add the definition of PROTO_LOCK

This one was added by commit daacf3664 ("BUG/MEDIUM: protocols: add a
global lock for the init/deinit stuff") but I forgot to add it to the
include file, breaking DEBUG_THREAD.

include/common/hathreads.h

@@ -562,6 +562,7 @@ enum lock_label {
 	AUTH_LOCK,
 	LOGSRV_LOCK,
 	DICT_LOCK,
+	PROTO_LOCK,
 	OTHER_LOCK,
 	LOCK_LABELS
 };
@@ -679,6 +680,7 @@ static inline const char *lock_label(enum lock_label label)
 	case AUTH_LOCK:            return "AUTH";
 	case LOGSRV_LOCK:          return "LOGSRV";
 	case DICT_LOCK:            return "DICT";
+	case PROTO_LOCK:           return "PROTO";
 	case OTHER_LOCK:           return "OTHER";
 	case LOCK_LABELS:          break; /* keep compiler happy */
 	};