When CREATE TEMPORARY TABLE .. SELECT is invoked from a stored function
which in turn is called from CREATE TABLE SELECT causes a memory leak
because the inner create temporary table overrides the outter extra_lock
reference when locking the table.

The solution is to simply not overrride the extra_lock by only using the
extra_lock for a non-temporary table lock.


mysql-test/r/create.result:
  Add test case result for Bug#21136
mysql-test/t/create.test:
  Add test case for Bug#21136
sql/sql_insert.cc:
  For temporary tables, store the lock data within the select_create class
  since tmp tables contents are not replicated. For "real" tables, store
  the lock data in the thread extra_lock pointer.