[Cython] libcpp container definition cleanup

[Yury V. Zaytsev]

Hi,

I've recently submitted a bunch of pull requests with cleanups for 
libcpp.string and libcpp.vector, most importantly fixing overloads taking 
and/or returning iterators and C++11 methods:

     https://github.com/cython/cython/pull/488

     https://github.com/cython/cython/pull/489

I might also manage to take a look at set / map / pair which we likewise 
need for our projects, but it would be great to get some feedback from the 
core developers first.

If the dominating opinion is that I'm strongly misguided in some way, I'd 
appreciate a short note before I invest more work into this :-)

Many thanks!

-- 
Sincerely yours,
Yury V. Zaytsev