JFX: all windows are resizable, even if the opposite is requested

[guiv42]

Some windows are supposed not to be resizable. See prototype to create a window, there is a boolean parameter "resizable"

This parameter is ignored in JFX configuration. A dedicated line in the code using this parameter has been commented out. But even when restoring this line, all windows remain resizable.

A simple example, see menu Help/About. Window is not resizable with SWT (as expected). But it is with JFX.