[Cython] ref-leak in 0.17

[Stefan Behnel]

Hi,

there is a reference leak in the new dict iteration code in 0.17:

http://trac.cython.org/cython_trac/ticket/790

I'll see if I can fix it and then release a pure bugfix 0.17.1 right
afterwards.

Please take a look at your own patch queues to see if there are any other
important bugs that you would like to see fixed in that release.

Stefan