Fixed bug #4976.
join_nested.result, join_nested.test:
  Added a test case for bug #4976.
sql_select.cc:
  Applied conversion from an outer join to an inner join 
  when the on expression does not depend on the outer table.
  It fixed bug #4976.


sql/sql_select.cc:
  Applied conversion from an outer join to an inner join 
  when the on expression does not depend on the outer table.
  It fixed bug #4976.
mysql-test/t/join_nested.test:
  Added a case test for bug #4976.
mysql-test/r/join_nested.result:
  Added a case test for bug #4976.
mysql-test/r/select.result:
  Fixed bug #4976.
mysql-test/r/join.result:
  Fixed bug #4976.