BUG #2397 "RENAME TABLES is not blocked by FLUSH TABLES WITH READ LOCK"
(added waiting for global_read_lock in mysql_rename_tables)


mysql-test/r/rename.result:
  added test for 
  BUG #2397 "RENAME TABLES is not blocked by FLUSH TABLES WITH READ LOCK"
mysql-test/t/rename.test:
  added test for 
  BUG #2397 "RENAME TABLES is not blocked by FLUSH TABLES WITH READ LOCK"
sql/sql_rename.cc:
  fixed 
  BUG #2397 "RENAME TABLES is not blocked by FLUSH TABLES WITH READ LOCK"
  (added waiting for global_read_lock)