[issue18986] Add a case-insensitive case-preserving dict

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

> Does it slow down regular dicts?

I were surprized, but yes. The ComplexPythonFunctionCalls test from pybench is 40% slower with ctransformdict.patch (and I still don't known why). With dict__transform__.patch it is only 2% slower. All other pybench tests are approximately equal.

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<http://bugs.python.org/issue18986>
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