validate if *_link highways end at the respective road type

[aceman]

I propose to add this new warning to the validator:
Check whether a way with highway=X_link is connected to a way with highway=X tag on at least one end OR another way with the same highway=X_link tag. Other ways of any type may intersect it (a junction) but one of the ends should finally lead to a highway of the respective type for which this one is a link.

[skyper]

Closed as duplicate of #9043.