Feedback on patch to fix change_column with :null => true

I just submitted a patch to fix an issue where using change_column
with :null => true on a formerly :null => false column does not work:

I'd like to get this into 2.1 and could use some +1 love. :slight_smile:

I've used this in production extensively with no issues, but couldn't
get tests integrated into AR's tree properly. I could use some simple
tips with this part (the mock DB's confused me).



Just need another +1 on the patch