Add a unit-test for longest-match-variant.
Add a unit-test for longest-match-variant.

The purpose of this unit-test is to make sure the fail-link
leading from terminal-state is correct. The fail-link leading
from terminal-state is not tested by the first-match-variant
(as in this variant, the fail-link of terminal state is not
 referenced at all).

cloudflare/lua-aho-corasick,cloudflare/lua-aho-corasick