Bug#669425: openturns: new upstream version

[D. Barbier]

[Moving discussion from 670066]

Do we want to build python-openturns against all available python
versions (which is smarter, but builds will take much longer), or do
we build only against the default version?
In the latter case, we should not let python-openturns Provides:
${python:Provides}.

IMO we can use the latter and see if builds run much faster with
CMake, in which case we may enable other python versions.

Denis