patch 8.2.0601: Vim9: :unlet is not compiled

Problem:    Vim9: :unlet is not compiled.
Solution:   Implement :unlet instruction and check for errors.
diff --git a/src/proto/evalvars.pro b/src/proto/evalvars.pro
index c53c115..e415932 100644
--- a/src/proto/evalvars.pro
+++ b/src/proto/evalvars.pro
@@ -21,6 +21,7 @@
 void list_hashtable_vars(hashtab_T *ht, char *prefix, int empty, int *first);
 void ex_unlet(exarg_T *eap);
 void ex_lockvar(exarg_T *eap);
+void ex_unletlock(exarg_T *eap, char_u *argstart, int deep, int glv_flags, int (*callback)(lval_T *, char_u *, exarg_T *, int, void *), void *cookie);
 int do_unlet(char_u *name, int forceit);
 void del_menutrans_vars(void);
 char_u *get_user_var_name(expand_T *xp, int idx);
diff --git a/src/proto/vim9compile.pro b/src/proto/vim9compile.pro
index b22bf98..76a9c99 100644
--- a/src/proto/vim9compile.pro
+++ b/src/proto/vim9compile.pro
@@ -1,13 +1,14 @@
 /* vim9compile.c */
 int check_defined(char_u *p, int len, cctx_T *cctx);
 char_u *skip_type(char_u *start);
-type_T *parse_type(char_u **arg, garray_T *type_list);
+type_T *parse_type(char_u **arg, garray_T *type_gap);
 char *vartype_name(vartype_T type);
 char *type_name(type_T *type, char **tofree);
 int get_script_item_idx(int sid, char_u *name, int check_writable);
 imported_T *find_imported(char_u *name, size_t len, cctx_T *cctx);
 char_u *to_name_const_end(char_u *arg);
 int assignment_len(char_u *p, int *heredoc);
+int check_vim9_unlet(char_u *name);
 void compile_def_function(ufunc_T *ufunc, int set_return_type);
 void delete_instr(isn_T *isn);
 void delete_def_function(ufunc_T *ufunc);