[Cython] import relative cimport

[Christoph Groth]

Hello,

I believe that relative cimports would be useful in Cython.  (For a
motivation, see my recent posting on cython-user
http://thread.gmane.org/gmane.comp.python.cython.user/7401)

So I tried to assess how much work it would be to implement that
feature, but that's a tough job as I do not have a good overview of
Cython's considerable code base.  Would allowing relative cimports be a
rather small thing comparable to commit 599c34053 which introduced
relative imports
(http://codereview.appspot.com/1734044/patch/2001/3001)?  Or are there
any issues that require serious refactoring?

Christoph