Optimization that transforms IN-predicate in IN-subselect made.

Trasformation goes that way:
a in (1,2) ->
a in (select * from (values ((1),(2))) as new_tvc)

Special variable that controlls optimization added.
Now optimization works only in several cases.
New tests added.

Old tests corrected. Now with TVC explain can be used. TVC also can be used in recursive CTEs.