SERIALIZABLE

Problem:

The documentation claims that WITH CONSISTENT SNAPSHOT will work for both
REPEATABLE READ and SERIALIZABLE isolation levels.  But it will work only
for REPEATABLE READ isolation level.  Also, the clause WITH CONSISTENT
SNAPSHOT is silently ignored when it is not applicable to the given isolation
level.  

Solution:

Generate a warning when the clause WITH CONSISTENT SNAPSHOT is ignored.

rb#2797 approved by Kevin.

Note: Support team wanted to push this to 5.5+.