Disabled std::log1p on Cygwin.

--HG--
extra : rebase_source : b4bf20443a53aadf30d0f74d9e269d770e0c5be2
Added alternative C++11 detection.

--HG--
extra : rebase_source : c1142bd3b18d8eb654e237ea65ce2d60f9dda3ab
Added copy constructor and assignment to DenseStorage.
Required by the standard even when its not used but elided.
Added a test for DenseStorage copying and assignment.

--HG--
extra : rebase_source : bde2fcbf66c0b9ce670afe9a22ef8cf177d3f5f9