[antlr-interest] executing actions during backtrack

[Micheal J]

> Currently there is no way to specify that an action must  
> execute even when backtracking.  That we still need a suggestion  
> for.  I almost wonder if it's a global flag like "always exec  
> actions" and then if you need a few not-executed, you can manually  
> gate with "if ( !guessing )".

As per my previous message: 

- Can backtracking still be nested?

- Can an action block execute multiple times due to [possibly nested]
backtracking?


Micheal