Category and interwiki links typically strip whitespace preceding them.

There's an odd special case, though: they *also* strip trailing newlines *if newlines are the only thing between the category/interwiki and the next link*.

This is arguably counterintuitive behavior, for example:

[[Category:Foo]] 

[[Foo]][[es:Alimento]]

[[Foo]]

renders as [[Foo]][[Foo]] due to this weird special case.

I think this behavior can be removed, but since the last time I touched this code my fix had to be reverted after unexpected consequences (T174639), I'm going to play it safe and make this a separate issue/patch set.