Cast time into timetz when the tzinfo field is set.

Hi! It seems that psycopg2 casts timezone-aware `datetime.time` objects into `time`, not `timetz` when they're compiled to SQL.
This patch fixes it and for this work I consulted the previous commit(5e3f240ac96ddb27dee4cb03f1c857be1ced8ff9) pertaining to the `timestamptz` which is very similar to current issue.