Remove redundant cab stretch facility

1. Initially OR stretched cab views to fit the window, so 4:3 cabs looked odd in wide-screen.
2. A scroll up-down was provided as an alternative with a Menu > Option > Video > "% cab 2D stretch"
3. Black bars were provided as another alternative, so 4:3 cabs could be full height and windows (e.g. F4) could lie outside cab.

Now we have 2 and 3, we don't need 1, so it should be removed along with the "% cab 2D stretch" control.

But see especially http://www.elvastower.com/forums/index.php?/topic/35301-menu-options/page__view__findpost__p__274197