Memory isn't initialized to zero by dbuf_queue_init(), causing

dbuf->length to be unitialized.
This wasn't an actual problem until yesterday in UnrealIRCd code,
since the whole client struct was initialized to zero, including
client->local->sendQ(->length) etc.
However, now we use the dbuf code elsewhere too (on the stack) and
3rd party modules can use it too, so fix this bug.

src/dbuf.c

@@ -58,6 +58,7 @@ static void dbuf_free(dbufbuf *ptr)
 
 void dbuf_queue_init(dbuf *dyn)
 {
+	memset(dyn, 0, sizeof(dbuf));
 	INIT_LIST_HEAD(&dyn->dbuf_list);
 }