Get nearest ranked user

[takoz53]

This should get the nearest two users by rank of another user.
E.g. person with rank 100 000 should yield back person with 99 999 and 100 001.
(basically 2xget_user requests with rank as parameter, yielding 2 user objects)

What would this be used for? (or at least for me):
I'd want to create Milestones for Players (e.g. you need x pp to reach y rank). Some people get motivated when they see these, so it would make them keep going.

Would help with comparing top plays etc. too, to give one player a goal to achieve new top plays.

Not sure what else one can use this for yet, but hopefully is enough reason to implement this.