patch 8.0.1449: slow redrawing with DirectX

Problem:    Slow redrawing with DirectX.
Solution:   Avoid calling gui_mch_flush() unnecessarily, especially when
            updating the cursor. (Ken Takata, closes #2560)
diff --git a/src/proto/term.pro b/src/proto/term.pro
index ef74f56..b0ad418 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -12,6 +12,7 @@
 char_u *tltoa(unsigned long i);
 void termcapinit(char_u *name);
 void out_flush(void);
+void out_flush_cursor(int force, int clear_selection);
 void out_flush_check(void);
 void out_trash(void);
 void out_char(unsigned c);