[antlr-interest] Faster expression parsing

[James Mansion]

Terence Parr wrote:
> This one is much more efficient but I am not sure it will show up  
> unless you have a huge input.
>   
Isn't the optimisation of:

    <some-elided-constructs> foo <some-more-elided-constructs> -> foo

to

    foo

something that antlr could do fairly easily?