patch 9.0.0603: with 'nosplitscroll' folds are not handled correctly

Problem:    With 'nosplitscroll' folds are not handled correctly.
Solution:   Take care of closed folds when moving the cursor. (Luuk van Baal,
            closes #11234)
diff --git a/src/proto/edit.pro b/src/proto/edit.pro
index f35ec1e..4513f4f 100644
--- a/src/proto/edit.pro
+++ b/src/proto/edit.pro
@@ -19,7 +19,9 @@
 void beginline(int flags);
 int oneright(void);
 int oneleft(void);
+linenr_T cursor_up_inner(win_T *wp, long n);
 int cursor_up(long n, int upd_topline);
+linenr_T cursor_down_inner(win_T *wp, long n);
 int cursor_down(long n, int upd_topline);
 int stuff_inserted(int c, long count, int no_esc);
 char_u *get_last_insert(void);