Ensured debug key handlers always exist when required

Before this commit the debug console's key handler wasn't added
to saved games which didn't have it because they weren't started
with debugging enabled and the debug script's key handler would
only be added to saved games when they were older than 85 and
debugging was enabled.
Merge pull request #354 from J-Shep/fixedMissingDebugKeyHandlers

Ensured debug mode key handlers always exist