[client] spice: new option spice:showCursorDot added

This option if disabled will prevent the client from showing a "dot"
cursor when the mouse is over the window, but the window is unfocused.

client/src/main.h

@@ -151,6 +151,7 @@ struct AppParams
   bool              rawMouse;
   bool              autoCapture;
   bool              captureInputOnly;
+  bool              showCursorDot;
 };
 
 struct CBRequest