Adjust the sqlite3 alter_column method to accept ignore_constraints
Adjust the sqlite3 alter_column method to accept ignore_constraints

Before this patch, migrations written to call alter_column() and
pass ignore_constraints=True (or =False) would work on
database backends like MySQL, but fail on sqlite3 with a TyepError:

   TypeError: alter_column() got an unexpected keyword argument 'ignore_constraints'

This patch fixes that.

matthiask/south,matthiask/south