Drift detection and a few updates

[Ian Gulliver]

The data drift detection code that Mikey Dickerson discussed in his MySQL Conference talk (http://en.oreilly.com/mysql2011/public/schedule/detail/17138) is now available at http://code.google.com/p/google-mysql-tools/source/browse/#svn%2Ftrunk%2Fdrift_lib. We still have some cleanup to do to merge it in to the other open source libraries, but the generate_checksums.py utility at the top level will write out checksums to the database. Remember, this code requires two functions from the Google MySQL patch to be present on the server.

Some other small changes:

• The permissions system now supports encrypted hashes in the permissions file.
• The SQL validator can now flag particular types of changes (e.g. DELETE) on particular tables.