patch 8.2.0185: Vim9 script: cannot use "if has()" to skip lines

Problem:    Vim9 script: cannot use "if has()" to skip lines.
Solution:   Evaluate constant expression at runtime.
diff --git a/src/proto/evalfunc.pro b/src/proto/evalfunc.pro
index 59ff35c..14a1a56 100644
--- a/src/proto/evalfunc.pro
+++ b/src/proto/evalfunc.pro
@@ -17,6 +17,7 @@
 win_T *get_optional_window(typval_T *argvars, int idx);
 void execute_redir_str(char_u *value, int value_len);
 void execute_common(typval_T *argvars, typval_T *rettv, int arg_off);
+void f_has(typval_T *argvars, typval_T *rettv);
 void mzscheme_call_vim(char_u *name, typval_T *args, typval_T *rettv);
 void range_list_materialize(list_T *list);
 float_T vim_round(float_T f);