Use enum wl_pointer_button_state instead of integer

Instead of using a uint32_t for state everywhere (except on the wire,
where that's still the call signature), use the new
wl_pointer_button_state enum, and explicit comparisons.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>
diff --git a/clients/clickdot.c b/clients/clickdot.c
index d935ae5..be4ee18 100644
--- a/clients/clickdot.c
+++ b/clients/clickdot.c
@@ -197,11 +197,12 @@
 static void
 button_handler(struct widget *widget,
 	       struct input *input, uint32_t time,
-	       uint32_t button, uint32_t state, void *data)
+	       uint32_t button,
+	       enum wl_pointer_button_state state, void *data)
 {
 	struct clickdot *clickdot = data;
 
-	if (state && button == BTN_LEFT)
+	if (state == WL_POINTER_BUTTON_STATE_PRESSED && button == BTN_LEFT)
 		input_get_position(input, &clickdot->dot.x, &clickdot->dot.y);
 
 	widget_schedule_redraw(widget);