Emit a long summary message to standard error (System.err) which
summarizes what was found in the specification, how many states were
produced, how many conflicts were found, etc.
Equality comparison -- here we only require the cores to be equal since
we need to do sets of items based only on core equality (ignoring
lookahead sets).
Put the (real) parse stack into error recovery configuration by
popping the stack down to a state that can shift on the special
error Symbol, then doing the shift.
This class implements a temporary or "virtual" parse stack that
replaces the top portion of the actual parse stack (the part that
has been changed by some set of operations) while maintaining its
original contents.