TurnMandatory

This method defines that turns from link1 is only allowed if the next turn is link2.

Internally this is translated into a number of turn restrictions. These are only applied at the end of link1, where it is actually possible to connect to link2.

If link1 and link2 are parallel links, you will get an error.

Syntax: TurnMandatory(index: integer; link1,link2: integer)