[Cython] releasing 0.18?

[Stefan Behnel]

Hi,

the current master doesn't really have the one new, great&shiny feature,
but I don't see a reason to keep the changes back that we have implemented
so far. Robert's const support and the integer overflow checks (assuming
that both are ready) are certainly worth it. Unless Mark's minivect changes
are ready to merge soonish, I don't think we should keep waiting for them.

So, what about getting the master ready for a release?

Note that this means that we need a couple of more comments in the
changelog, as well as documentation for the things that need it (const?).

Stefan