share/cairo-util: Use wl_pointer_button_state enum directly

This silences two warnings:

clients/window.c:2450:20: warning: implicit conversion from enumeration
type 'enum wl_pointer_button_state' to different enumeration type 'enum
frame_button_state' [-Wenum-conversion]
                                              button, state);
                                                      ^~~~~

clients/window.c:2453:15: warning: implicit conversion from enumeration
type 'enum wl_pointer_button_state' to different enumeration type 'enum
frame_button_state' [-Wenum-conversion]
                                                button, state);
                                                        ^~~~~

Warning produced by Clang 3.8.

Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Giulio Camuffo <giuliocamuffo@gmail.com>
diff --git a/xwayland/window-manager.c b/xwayland/window-manager.c
index 4fab602..0e26d7c 100644
--- a/xwayland/window-manager.c
+++ b/xwayland/window-manager.c
@@ -1759,7 +1759,7 @@
 	struct weston_pointer *pointer;
 	struct weston_wm_window *window;
 	enum theme_location location;
-	enum frame_button_state button_state;
+	enum wl_pointer_button_state button_state;
 	uint32_t button_id;
 
 	wm_log("XCB_BUTTON_%s (detail %d)\n",
@@ -1777,7 +1777,8 @@
 	pointer = weston_seat_get_pointer(seat);
 
 	button_state = button->response_type == XCB_BUTTON_PRESS ?
-		FRAME_BUTTON_PRESSED : FRAME_BUTTON_RELEASED;
+		WL_POINTER_BUTTON_STATE_PRESSED :
+		WL_POINTER_BUTTON_STATE_RELEASED;
 	button_id = button->detail == 1 ? BTN_LEFT : BTN_RIGHT;
 
 	/* Make sure we're looking at the right location.  The frame