Added a test case for bug #4922.
sql_select.cc:
  Blocked an optimization performed by join_read_const_table when
  applied to an inner table of a nested outer join.
  It was done to fix bug #4922.
sql_yacc.yy:
  Fixed a typo bug in the rule for join_table.


sql/sql_yacc.yy:
  Fixed a typo bug in the rule for join_table.
sql/sql_select.cc:
  Blocked an optimization performed by join_read_const_table when
  applied to an inner table of a nested outer join.
  It was done to fix bug #4922.
mysql-test/t/join_nested.test:
  Added a test case for bug #4922.
mysql-test/r/join_nested.result:
  Added a test case for bug #4922.