Fixed #8510 -- Allow both strings (mostly for the admin) and integers to be

used in "month" and "day" filters on date/datetime fields. Without this commit,
SQLite behaved inconsistently after [8494].


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8526 bcc190cf-cafb-0310-a4f2-bffc1f526a37