allow_wraparound incorrectly documented

[Andrew Cooke]

The documentation for Counter says:

allow_wraparound (boolean) - If True, the function will raise an OverflowError exception as soon as the counter wraps around. If False (default), the counter will simply restart from zero.

Which is very confusing. If the text is correct then setting this to true (ie setting ALLOW to TRUE) means that wraparound is DISALLOWED. The implementation is at the C level so I haven't looked or tested, but at the moment it's not clear if the docs are wrong, or
if the naming of the parameter is just monumentally dumb.

Marking this as a security vulnerability because if you get wraparound when you're not expecting it you could have duplicate streams.

[Andrew Cooke (ato2gx513oupn-andrew-n1by9anq91ai4)]

So I went and wrote some tests. The documentation is incorrect; the parameter name is correct. So it should read:

allow_wraparound (boolean) - If *False* (default), the function will raise an OverflowError exception as soon as the counter wraps around. If True, the counter will simply restart from zero.

Note that the default (correctly, imho) remains False, so has shifted in the description above.

[Andrew Cooke (ato2gx513oupn-andrew-n1by9anq91ai4)]

Removed security marker after seeing no-one else used it for this project.

[Legrandin (gooksankoo)]

A fix is available here:

https://github.com/Legrandin/pycrypto/commit/7a720a6cd9254930ea4aa334610393dc9a420213

Now it reads:

allow_wraparound (boolean)
If *True*, the counter will automatically restart from zero after
reaching the maximum value (``2**nbits-1``).
If *False* (default), the object will raise an *OverflowError*.

[Darsey Litzenberger (dlitz)]

Pull request: https://github.com/dlitz/pycrypto/pull/43

Fix committed: https://github.com/dlitz/pycrypto/commit/f73d0a11697e2be0a3a1819fdb91a5dadc4e6af8