Fix curses cursor keys

My change to allow fuzzer run in curses caused the cursor keys
to not work (eg. paging through menus with left and right cursor),
so fix that.

include/wincurs.h

@@ -151,6 +151,7 @@ extern boolean curses_map_borders(int *sx, int *sy, int *ex, int *ey,
 
 /* cursmisc.c */
 
+extern int curses_getch(void);
 extern int curses_read_char(void);
 extern void curses_toggle_color_attr(WINDOW *win, int color, int attr,
                                      int onoff);