patch 9.0.0481: in :def function all closures in loop get the same variables

Problem:    In a :def function all closures in a loop get the same variables.
Solution:   Use a separate list of variables for LOADOUTER and STOREOUTER.
            Not copied at end of loop yet.
diff --git a/src/proto/vim9execute.pro b/src/proto/vim9execute.pro
index b8360c5..e624f55 100644
--- a/src/proto/vim9execute.pro
+++ b/src/proto/vim9execute.pro
@@ -9,7 +9,7 @@
 int add_defer_function(char_u *name, int argcount, typval_T *argvars);
 char_u *char_from_string(char_u *str, varnumber_T index);
 char_u *string_slice(char_u *str, varnumber_T first, varnumber_T last, int exclusive);
-int fill_partial_and_closure(partial_T *pt, ufunc_T *ufunc, ectx_T *ectx);
+int fill_partial_and_closure(partial_T *pt, ufunc_T *ufunc, short loop_var_idx, short loop_var_count, ectx_T *ectx);
 int may_load_script(int sid, int *loaded);
 typval_T *lookup_debug_var(char_u *name);
 int may_break_in_function(ufunc_T *ufunc);