Issue:Category:New format symbols: %PREV% and %NEXT%

Description:	%PREV% returns "previous XX", %NEXT% returns "next XX"
Extension / Version:	DPL   /   ?
Type / Status:	Change Request   /   open

Problem

I absolutely fail setting up a template for navigating through a long result list. It would be very handy to just use %PREV% and %NEXT% in the resultsheader or resultsfooter. They sinply return "previous XX" and "next XX" and can be freely formatted by the user, e.g. to addapt the wiki style (previous 200) (next 200) or create an own style.
They are only linked if there is something to navigate to.

As long as you can't use %PAGES% or {{{%PAGES%}}} inside {{#ifexpr: or {{#expr: it's impossible to set up logical prev / next links, esp. since you may also want to use %PAGES% and %TOTALPAGES% together which is another bug.

Btw: Does a working template exists here as example? Didn't find any. Please let me now.