Make sure no prototype exists for callback function

Implemented my simple NoAutoProto macro trick for the callback function,
so that no automatic prototype would be generated. Apparently this was
necessary for my hunt-the-wumpus version when you turn the menu option
off by commenting out the appropriate #defines; somehow Visual Micro
(and perhaps Arduino IDE, I didn't check) would still try to parse the
LcdMenu.h file even though it was #ifdef'd out, and would generate an
automatic prototype and fail, of course, because MenuShow is an
undefined type when the automatic prototypes are compiled (I still can't
believe how this stupid non-disable-able "feature" ended up in the
Arduino software).