title: Rails 3 migration for adding unsigned int column
body: <p>I would like to generate a migration to add a column to a table which has a data type of unsigned int. I wish to use it to store IP addresses as mentioned here in <a href="https://blogs.law.harvard.edu/zeroday/2009/04/04/storing-ip-addresses-in-mysql-with-rubyrails/" rel="nofollow noreferrer">this article</a>.</p>
  
  <p>I came across <a href="https://stackoverflow.com/questions/4156772/unsigned-int-field-in-a-ruby-on-rails-migration">this question</a> but it will make the migration database dependent, any idea how to do it in a better way?</p>