WL#5370 Keep forward-compatibility when changing

        'CREATE TABLE IF NOT EXISTS ... SELECT' behaviour
BUG#47132, BUG#47442, BUG49494, BUG#23992 and BUG#48814 will disappear
automatically after the this patch.
BUG#55617 is fixed by this patch too.
            
This is the 5.5 part.
It implements:
- 'CREATE TABLE IF NOT EXISTS ... SELECT' statement will not insert
  anything and binlog anything if the table already exists.
  It only generate a warning that table already exists.
- A couple of test cases for the behavior changing.

1 files changed, 1 insertions, 1 deletions

diff --git a/mysql-test/r/union.result b/mysql-test/r/union.result
index 2080f4e8b61..33fc4333d1c 100644
--- a/mysql-test/r/union.result
+++ b/mysql-test/r/union.result
@@ -428,7 +428,7 @@ ERROR 42000: Incorrect usage/placement of 'SQL_CALC_FOUND_ROWS'
 create temporary table t1 select a from t1 union select a from t2;
 drop temporary table t1;
 create table t1 select a from t1 union select a from t2;
-ERROR HY000: You can't specify target table 't1' for update in FROM clause
+ERROR 42S01: Table 't1' already exists
 select a from t1 union select a from t2 order by t2.a;
 ERROR 42S22: Unknown column 't2.a' in 'order clause'
 drop table t1,t2;