Small fix for extracting mouse coordinates on Windows, in a way that will always…

Small fix for extracting mouse coordinates on Windows, in a way that will always work with multiple monitors.
This is the way recommended by Microsoft.

modules/highgui/src/window_w32.cpp

@@ -1474,8 +1474,8 @@ static LRESULT CALLBACK HighGUIProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM
             if( uMsg == WM_LBUTTONUP || uMsg == WM_RBUTTONUP || uMsg == WM_MBUTTONUP )
                 ReleaseCapture();
 
-            pt.x = LOWORD( lParam );
-            pt.y = HIWORD( lParam );
+            pt.x = GET_X_LPARAM( lParam );
+            pt.y = GET_Y_LPARAM( lParam );
 
             GetClientRect( window->hwnd, &rect );
             icvGetBitmapData( window, &size, 0, 0 );