patch 9.0.2016: Vim9: assignment operators don't work for class vars

Problem:  Vim9: assignment operators don't work for class vars
Solution: implement it

closes: #13306

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/vim9class.c b/src/vim9class.c
index 0cb353b..5dda700 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -2032,7 +2032,7 @@
  * Set *p_m ocmmember_T if not NULL
  */
     type_T *
-class_member_type(
+oc_member_type(
     class_T	*cl,
     int		is_object,
     char_u	*name,
@@ -2060,7 +2060,7 @@
  * Given a class or object variable index, return the variable type
  */
     type_T *
-class_member_type_by_idx(
+oc_member_type_by_idx(
     class_T	*cl,
     int		is_object,
     int		member_idx)