Rotate test

[Paolo Carlini]

Christopher Jefferson wrote:
> This patch adds a new test for rotate, which much more carefully
> checks various corner cases. It doesn't reveal any bugs in either
> current, or future patches, but it makes me much more comfortable they
> work correctly!
Excellent, applied.

Please let me know asap if you can audit the new C++0x algos vs
parallel-mode, it's important. Thanks.

Paolo.