patch 8.1.0523: opening window from quickfix leaves empty buffer behind

Problem:    Opening window from quickfix leaves empty buffer behind.
Solution:   Add qf_jump_newwin(). (Yegappan Lakshmanan, closes #2574)
diff --git a/src/proto/quickfix.pro b/src/proto/quickfix.pro
index d58e92f..a71f343 100644
--- a/src/proto/quickfix.pro
+++ b/src/proto/quickfix.pro
@@ -4,6 +4,7 @@
 void check_quickfix_busy(void);
 void copy_loclist_stack(win_T *from, win_T *to);
 void qf_jump(qf_info_T *qi, int dir, int errornr, int forceit);
+void qf_jump_newwin(qf_info_T *qi, int dir, int errornr, int forceit, int newwin);
 void qf_list(exarg_T *eap);
 void qf_age(exarg_T *eap);
 void qf_history(exarg_T *eap);