openCypher label predicates in WHERE clauses were a parse error
("expected token type 67, got 73"). Parse `var:Label` in the WHERE leaf as
a condition with op=HAS_LABEL/value=Label, and evaluate it against the bound
node label in eval_condition (honoring NOT). Composes with AND/OR and works
in count(...) queries.
Unit test covers true/false/negated label predicates; smoke suite adds a
query_graph WHERE-label check.
Martin Vogel
b30e6d6443