Change key/button grab bindings to take unsigned state

'state' here meaning 'is it up or down?', obviously.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>
diff --git a/clients/window.h b/clients/window.h
index a2a7880..d2abb3d 100644
--- a/clients/window.h
+++ b/clients/window.h
@@ -190,7 +190,8 @@
 				       int32_t x, int32_t y, void *data);
 typedef void (*widget_button_handler_t)(struct widget *widget,
 					struct input *input, uint32_t time,
-					int button, int state, void *data);
+					int button, uint32_t state,
+					void *data);
 
 struct window *
 window_create(struct display *display);