wayland: Implement maximized state

src/wl_platform.h

@@ -83,6 +83,7 @@ typedef struct _GLFWwindowWayland
 {
     int                         width, height;
     GLFWbool                    visible;
+    GLFWbool                    maximized;
     struct wl_surface*          surface;
     struct wl_egl_window*       native;
     struct wl_shell_surface*    shell_surface;