[mojosetup] Expose the runScript interface to allow non LUA scripts to be run

[Jeremy White]

> Okay, next time you sync up, please change any existing calls to this in
> your existing installers. If they passed 0 for /dev/null, this will
> translate to true, which isn't what you want; Lua treats false and nil
> as boolean false, and everything else--including zero--as true. You have
> been warned!.

Thanks for the warning; probably saved my bacon.  Of course, that won't
help me the next time and I've forgotten... <grin>.

Cheers,

Jeremy