Add optional virtual on-screen keyboard
This is for anyone using a joystick including Xbox or other console users. The keyboard should be displayed when a menu option is selected that requires keyboard input such as player name or save name. It should also be displayed when a user needs to enter text in-game such as when entering text in the chat line. It should also be able to be displayed using a bind so that a user can bring it up and enter cheat codes while in-game. There should be a menu option to enabled/disable the feature and it should be defaulted to off with the exception of game consoles where it should be defaulted to on.
Patch submission: https://github.com/JohnnyonFlame/odamex/commit/a6746c1edd0300a7e3ef37f681d4052c7441f99c