This PR includes:
-- a test+fix for #1262
-- a fix for SQL Server settings default on alter-column (may apply to Postgresql/MySql backends as well)
-- A fix for the test_alter_unique() test -- some sorting out of transactions, and changing an altered IntegerField column type from CharField to PositiveIntegerField so that Oracle is appeased.
I was in a bit of a rush earlier and forgot to mention: After this PR, SQLite, MSSQL and Oracle all pass under Django 1.4. Under 1.5, Oracle has an issue with CharField <-> TextField changes (which also exists before the PR, AFAICT). I'll take care of that later.