True if State is an opaque value representing the regular expression
state described by OptionSugar and CapturesSugar. OptionSugar
should be a list or an atom. If it's an atom it should
be something like 'ims', 'xi', etc. Fails if OptionSugar contains an
unknown option.
Adds Capture to State0 giving a new State. Capture may be
Name=Value or just Value. Pushing a named capture pushes both a
named and a numbered capture.