with-eval-after-load shim not quite right

After reading https://github.com/lunaryorn/blog/blob/master/posts/introducing-with-eval-after-load.md, I realized taking the `with-eval-after-load` definition directly from Emacs 24.4 as I suggested in https://github.com/dimitri/el-get/pull/1976#issuecomment-61371301 is not quite right: the additional `funcall` as used in that blog post is needed.