Divide by zero memory leak (Trac #830)

_Original ticket http://projects.scipy.org/numpy/ticket/830 on 2008-06-24 by @cournape, assigned to @cournape._

See ticket 493 from scipy trac

Dividing by zero (e.g. 1/scipy.float64(0.)) yields scipy.inf as it is supposed to, but leaks memory in the process.

I'll attach a sample program where memory usage grows without bound.

```
#!python
import scipy
x = scipy.float64(0.)
while 1:
    1/x
```
