Minor performance improvement: Add faster variant of eat()

and a faster version of eatOptional().

eat() is called frequently when converting lexed tokens to values,
and often with a single token type. Varargs and array counting would
slow that down.

validatiion/ParserPerformance sped up from 0.581 to 0.574 seconds (1%).
(Added a loop to run on 100 files 10 times, divided by 10, took best times)

Author: TysonAndre