Fix leaky token abstraction

[rafe]

Don't force the use of parentheses for regular expression repeat notation. That is, don't force this:

(?: optional_word )?

Allow the more natural notation:

optional_word?

So anytime I find a *, +, {x,y} not preceded by a closing parenthesis automatically add the surrounding (?: ... )

[rafe]

Moving issue to new stacked-regex repository