Fix application window not listed in taskbar (X11)

* for executable
* for editor and exported executable (on older Cinnamon versions)

platform/x11/context_gl_x11.cpp

@@ -191,6 +191,7 @@ Error ContextGL_X11::initialize() {
 
 	swa.colormap = XCreateColormap(x11_display, RootWindow(x11_display, vi->screen), vi->visual, AllocNone);
 	x11_window = XCreateWindow(x11_display, RootWindow(x11_display, vi->screen), 0, 0, OS::get_singleton()->get_video_mode().width, OS::get_singleton()->get_video_mode().height, 0, vi->depth, InputOutput, vi->visual, valuemask, &swa);
+	XStoreName(x11_display, x11_window, "Godot Engine");
 
 	ERR_FAIL_COND_V(!x11_window, ERR_UNCONFIGURED);
 	set_class_hint(x11_display, x11_window);