Bug #10308: Parse 'purge master logs' with subselect correctly.
subselect.test:
  Bug #10308: Test for 'purge master logs' with subselect.
subselect.result:
  Bug #10308: Test result for 'purge master logs' with subselect.


mysql-test/r/subselect.result:
  Bug #10308: Test result for 'purge master logs' with subselect.
mysql-test/t/subselect.test:
  Bug #10308: Test for 'purge master logs' with subselect.
sql/sql_yacc.yy:
  Bug #10308: Parse 'purge master logs' with subselect correctly.