Add a "Control vehicle" menu entry to the examine menu.

I actually wanted to integrate every entry in the vehicle control menu
Inside the examine menu, but that's a lot more of code inside the pickup()
function which should be split in parts.

There are some things that should be cleaned up, the menu should be
in examine() instead of pickup(), for starters.

I kept this simple, it's handy and doesn't change things too much.

If the player is drivng the vehicle, "e" doesn't ask for a direction, similar to how "^" works.