MDEV-16414 Add type_handler_xpath_nodeset and remove XPATH_NODESET

sql/item.h

@@ -740,7 +740,6 @@ class Item: public Value_source,
              FIELD_VARIANCE_ITEM, INSERT_VALUE_ITEM,
              SUBSELECT_ITEM, ROW_ITEM, CACHE_ITEM, TYPE_HOLDER,
              PARAM_ITEM, TRIGGER_FIELD_ITEM,
-             XPATH_NODESET, XPATH_NODESET_CMP,
              EXPR_CACHE_ITEM};
 
   enum cond_result { COND_UNDEF,COND_OK,COND_TRUE,COND_FALSE };
@@ -1349,7 +1348,7 @@ class Item: public Value_source,
   {
     return type_handler()->Item_val_bool(this);
   }
-  virtual String *val_nodeset(String*) { return 0; }
+  virtual String *val_raw(String*) { return 0; }
 
   /*
     save_val() is method of val_* family which stores value in the given