patch 9.0.0350: :echowindow does not work in a compiled function

Problem:    :echowindow does not work in a compiled function.
Solution:   Handle the expression at compile time.
diff --git a/src/proto/ex_docmd.pro b/src/proto/ex_docmd.pro
index 28f4c43..f5d7a48 100644
--- a/src/proto/ex_docmd.pro
+++ b/src/proto/ex_docmd.pro
@@ -55,6 +55,7 @@
 void do_sleep(long msec, int hide_cursor);
 void ex_may_print(exarg_T *eap);
 void ex_redraw(exarg_T *eap);
+void redraw_cmd(int clear);
 int vim_mkdir_emsg(char_u *name, int prot);
 FILE *open_exfile(char_u *fname, int forceit, char *mode);
 void update_topline_cursor(void);