nitcc: improve displaying of firsts/afters/lookahead

since thez are now Items, not Tokens

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: improve auto-dangling

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: add test/conflict-bracket and test/conflitc-dangling

Signed-off-by: Jean Privat <jean@pryen.org>