[Tagging] Implied oneway tag for highway=*_link, wiki edits

[Alessandro Rubini]

> The disadvantage of explicit tagging for everything is massive
> duplication of information.

This I agree with.

> It also means that newcomers may not quite
> get the tagging right, because they assume that a road type which is
> inherently one-way doesn't need explicit tagging.

I don't think there are road types that are inherently one-way, besides
roundabouts.

This is a two-way motorway link, for example:

http://maps.google.it/?ie=UTF8&ll=45.249774,9.044243&spn=0.002761,0.004914&t=k&z=18

/alessandro