FeatureComplete: implement links predicate

[mcharsley]

[hanbings]

Hi! Are you still interested in this issues? It looks like it already has some level of implementation:

$ ./target/debug/find . -links 1
$ ./target/debug/find . -links +0
$ ./target/debug/find . -links -2

[tavianator]

This was done by https://github.com/uutils/findutils/pull/167, I just forgot to add the "closes #10" tag :)

[hanbings]

Thanks. Now let's close it!