Defaults modified from original: alpha=200, key=F10

This is just a chat window with the / text pre-loaded.

This allows us to map the keys which are not considered in
irrlicht's EKEY_CODE system, such as \, [, /, ] etc.

Constify keycode and move the static array of localizable names from the
guiKeyChangeMenu header to the implementation file, changing its name.

At least two reasons for this:
* activeKey is treated as signed (check for sign, assign -1, etc)
* the ID retrieved from Irrlicht's events are signed

now translated if set to a button

configwriting/saving isn't complete and will break your config if you use fancy keys

configwriting/saving isn't complete and will break your config if you use fancy keys