[1.0.X] Make sure that all uses of max_length in the test suite use values...

[1.0.X] Make sure that all uses of max_length in the test suite use values smaller than 255. If we use max_length > 255 the test suite can't be run on MySQL 4. Backport of [10697] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10698 bcc190cf-cafb-0310-a4f2-bffc1f526a37