Cxx03

I've been eyeing at libsimdpp a potential way to unify my project's jumbled mix of various non-vectorized, SSE2, SSSE3, and NEON implementations.  This project can't require C++11 yet, and probably won't be able to for several years.

Do you feel very strongly that libsimdpp must stay as a C++11 codebase?

This is an incomplete patch with some of the changes that might be necessary if you were to drop back to targeting an older version of C++.  I still need to remove lambdas, fix up more returns like in c586a73, find an alternative for std::array, and I'm sure more.  I'm happy to do all this work and test it however you recommend.  But I figured at this point there are enough changes here that you'd probably have an opinion on whether you'd want to upstream C++<11 support and live with the code like this, or if you want to stick to C++11.

Mike