to insert view's subqueries into select_lex->slave(->next)* chain. 
In case a join has several such views, don't add the same subqueries several times
(this forms a loop on the above chain which breaks many parts of the code)


mysql-test/r/view.result:
  Testcase for BUG#8490
mysql-test/t/view.test:
  Testcase for BUG#8490