added database.txt documentation; currently only describing Django-related
features of MySQL versions.
As of this commit, there are four known test failures due to (a) no transaction
support with MyISAM storage engine and (b) MySQLdb automatically creating
decimal types for Django's "float" field.
git-svn-id: http://code.djangoproject.com/svn/django/trunk@4724 bcc190cf-cafb-0310-a4f2-bffc1f526a37
Russell Keith-Magee
Malcolm Tredinnick
Adrian Holovaty