Retrieve SDL controller mapping from environment variable.
This is the environment variable defined by the official SDL2 Gamepad Tool.

Removed some apparently unnecessary logic which will only allow the look-right driveby animation to occur if you are in 1st person mode or if there is no passenger.

Added gamepad support.
Open/close the menu by holding R1/RB & Triangle/Y.
You can select menus and submenus and menu items with the cross/A button, and navigate backward with B/Circle.
Also you can hit circle at the root menu to close it.
Toggle menuitems with the cross/A button, or toggle backward with X/Square.

Largely operates the same as the games frontend/pause menu.

Todo:
Properly implement autoscrolling for the gamepad. Ie, holding the stick or dpad down to quickly scroll through the menu / options
Also, am only able to test on my linux/glfw setup. Might be handy to get some feedback on whether this is working as intended elsewhere

one character got flubbed on its way over.