'Renames the column of \'table_name\' from \'old\' to \'new\'.
WARNING - This isn\'t transactional on MSSQL!'

@copy_column_constraints
@delete_column_constraints
def rename_column(self, table_name, old, new):

    if (old == new):
        return
    params = (table_name, self.quote_name(old), self.quote_name(new))
    self.execute(("EXEC    sp_rename    '%s.%s',    %s,    'COLUMN'" % params))
