current spec fragment doesn't use ExponentiationExpression

[saurik]

The current specification draft defines "ExponentiationExpression" but fails to use it anywhere ;P. In #9 (comment), it was described that -x**-y should be parsed as -(x**(-y)). It is honestly not clear to me what minimal typo could have been made in the current specification draft to fix it so that that is the behavior. I feel like, "at best" there must have been multiple typos, and "at worst" the specification draft is broken; though maybe I'm just missing something obvious that allows it to be corrected with one token.