patch 9.0.1982: vim9: clean up from v9.0.1955

Problem:  vim9: clean up from v9.0.1955
Solution: Fix a few remaining issues, improve error message

- Use `cl_exec`, the executing class, to check permissions in `get_lval()`.
- Handle lockvar of script variable from class.
- Add 'in class "Xxx"' to e_cannot_access_private_variable_str.

closes: #13222

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Ernie Rael <errael@raelity.com>
diff --git a/src/globals.h b/src/globals.h
index 9937839..d54e311 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1953,8 +1953,7 @@
 #ifdef FEAT_EVAL
 EXTERN int  input_busy INIT(= 0);   // when inside get_user_input() then > 0
 
-EXTERN typval_T	*lval_root INIT(= NULL);
-EXTERN int	lval_root_is_arg INIT(= 0);
+EXTERN lval_root_T	*lval_root INIT(= NULL);
 #endif
 
 #ifdef FEAT_BEVAL_TERM