check correctness of errors before updating them so we don't get bogus errors added

	find . -name '[^.]*.[ch]' | xargs etags -a

errors:

	$(PERL) util/ck_errf.pl -strict */*.c */*/*.c

	$(PERL) util/mkerr.pl -recurse -write

	(cd engines; $(MAKE) PERL=$(PERL) errors)

	$(PERL) util/ck_errf.pl -strict */*.c */*/*.c

stacks:

	$(PERL) util/mkstack.pl -write