Fix when k-step ahead predictions are stored, with k>1, and one-step-ahead...

Fix when k-step ahead predictions are stored, with k>1, and one-step-ahead predictions has to be stored in stock1.

git-svn-id: https://www.dynare.org/svn/dynare/branches/4.0@2508 ac1d8469-bf42-47a9-8791-bf33cf982152