Linkify another changelog entry

docs/announce/2015.03.md

@@ -32,7 +32,7 @@ Some of the new compiler features added to this release include:
 + Implement `method ^foo($) { ... }` syntax.
 + Implemented [PairMap](http://doc.perl6.org/type/PairMap) (the simple case only, for now).
 + Implemented `.antipairs` (pairs with value => key).
-+ Implemented `.pairup` for creating pairs from lists.
++ Implemented [pairup](http://doc.perl6.org/type/Any#method_pairup) for creating pairs from lists.
 + Implemented `LEXICAL`, `OUTERS` and `CALLERS` pseudo-packages
 + Add `array[T]`, usable for native `int`/`num` (MoarVM only for now)
 + Other native improvements, e.g. `my int $a; $a++`