Remove leftover of fds_in_tail hack

It's breaking the case of multiple fds in one buffer.

TODO

@@ -8,7 +8,10 @@ Core wayland protocol
 
  - The message format has to include information about number of fds
    in the message so we can skip a message correctly.  Or we should
-   just give up on trying to recover from unknown messages.
+   just give up on trying to recover from unknown messages.  We need
+   to make sure you never get a message from an interface you don't
+   know about (using per-client id space and subscribe) or include
+   information on number of fds, so marshalling logic can skip.
 
  - generate pointer_focus (and drag focus) on raise/lower, move
    windows, all kinds of changes in surface stacking.

wayland/connection.c

@@ -58,7 +58,6 @@ struct wl_closure {
 struct wl_connection {
 	struct wl_buffer in, out;
 	struct wl_buffer fds_in, fds_out;
-	int fds_in_tail;
 	int fd;
 	void *data;
 	wl_connection_update_func_t update;
@@ -190,7 +189,6 @@ void
 wl_connection_consume(struct wl_connection *connection, size_t size)
 {
 	connection->in.tail += size;
-	connection->fds_in.tail = connection->fds_in_tail;
 }
 
 static void