[web2py] Bug in dal.py function _count

[Harkirat]

The _count feature which is supposed to generate raw SQL is not
working.
I traced it to an error in the dal.py on line 4481. The function
currently is

def _count(self):
        return self.db._adapter.COUNT(self.query)

should be

def _count(self):
        return self.db._adapter._count(self.query)