Use the proper macro to convert a bool to a Datum.

The original coding was
	var->value = (Datum) state;
which is bogus, and then in commit 2f0f7b4b
it was "corrected" to
	var->value = PointerGetDatum(state);
which is a faithful translation but still wrong.

This seems purely cosmetic, though, so no need for a back-patch.

Pavel Stehule