fix customize controls menu (deactivate IFeel settings when not on PL…

[Manuel-K]

…ATFORM_WIN32)

Followed the suggestion by @rohit-n in #33

This makes the control menu work on Linux.

Note: There is another problem: If the mouse wheel is used to change the page, the input gets stuck i.e. all controls that you customize get set to either “Mouse Wheel Up“ or “Mouse Wheel Down”.