When calling the indices method of a slice object with a negative stop
larger in absolute value than the length passed, the returned stop value
is always -1.  It should be 0 when the step is positive.

Current behavior:

>>> slice(-10).indices(11)
(0, 1, 1)
>>> slice(-10).indices(10)
(0, 0, 1)
>>> slice(-10).indices(9)
(0, -1, 1)
>>> slice(-10).indices(8)
(0, -1, 1)

Expected behavior:

>>> slice(-10).indices(11)
(0, 1, 1)
>>> slice(-10).indices(10)
(0, 0, 1)
>>> slice(-10).indices(9)
(0, 0, 1)
>>> slice(-10).indices(8)
(0, 0, 1)

The patch I submit trivially fixes this while preserving the expected -1
when the step is negative like in:

>>> slice(None, -10, -1).indices(8)
(7, -1, -1)

This issue affects python 2.5 and 2.6 at least.  I did not test with
other versions.