Fix for memory leak which was introduced by patch improving locking in SP.

Made mysql_make_view() to call destructor for st_lex_local objects before
throwing them away (this happens in case of error).


sql/sql_lex.h:
  Made LEX's destructor virtual to be able properly destroy objects
  of inherited classes (i.e. of st_lex_local).
sql/sql_view.cc:
  mysql_make_view():
    We should call destructor for st_lex_local object before throwing
    it away.

sql/sql_view.cc

@@ -854,6 +854,7 @@ ok2:
 err:
   if (arena)
     thd->restore_backup_item_arena(arena, &backup);
+  delete table->view;
   table->view= 0;	// now it is not VIEW placeholder
   thd->lex= old_lex;
   DBUG_RETURN(1);