Installation does not work correctly with certain versions of MySQL

When installing Boost on servers with certain versions of MySQL, the 'boost_cache' and 'boost_crawler' tables aren't created. This is a result of these versions of MySQL not allowing default values for text columns.

I've created a patch that removes the default values from the database schema for the three columns that prevent these tables from being created. There is also an update function that removes the default values on existing installations to prevent data loss if someone upgrades to a version of MySQL that doesn't permit default text values. The update function doesn't address existing installations that are missing tables or columns.

I doubt it's a common issue, but anyone who has an undiagnosed issue should check their log entries for php errors due to these tables missing.

Version info:
MySQL 5.1.30
PHP 5.2.10
Apache 2.2.11
Drupal 6.15