Fix for BUG#20522 "RBR: CREATE TEMPORARY TABLE SELECT writes to binlog

though unneeded". It's indeed unneeded, as slave is only interested in
permanent tables, and permanent tables don't depend on temporary tables
when in row-based binlogging mode. And other CREATE TEMPORARY TABLE
(referring no table or with LIKE) already don't write the CREATE to
binlog in row-based mode. 


mysql-test/r/rpl_row_create_table.result:
  result update (note that no lines appear in SHOW BINLOG EVENTS further below, which is how we
  see the bug is fixed)
mysql-test/t/rpl_row_create_table.test:
  testing if a CREATE TEMPORARY TABLE SELECT goes to binlog (it should not)
  when in row-based binlogging mode. A few lines after, there is a SHOW
  BINLOG EVENTS; before the bugfix it showed the CREATE TEMPORARY TABLE.
sql/sql_class.h:
  a method to access select_create::create_info from outside of select_create
  ("read-only" access). Making get_thd() "read-only" too.
sql/sql_insert.cc:
  The function (hook) which writes CREATE TABLE to binlog when in row-based
  binlogging mode, for CREATE TABLE SELECT, now does nothing if the table
  is temporary (as in row-based mode, temp tables are not replicated).
  This is consistent with CREATE TEMPORARY TABLE LIKE and
  CREATE TEMPORARY TABLE, which don't write any CREATE to binlog in row-based
  mode.

mysql-test/r/rpl_row_create_table.result

@@ -178,6 +178,7 @@ CREATE TABLE t8 LIKE t4;
 CREATE TABLE t9 LIKE tt4;
 CREATE TEMPORARY TABLE tt5 LIKE t4;
 CREATE TEMPORARY TABLE tt6 LIKE tt4;
+CREATE TEMPORARY TABLE tt7 SELECT 1;
 **** On Master ****
 SHOW CREATE TABLE t8;
 Table	t8