[Pyrex] Cython 0.9.6.8 released

[Robert Bradshaw]

Cython 0.9.6.8 is released.

The primary feature of this release is merging in the changes/ 
bugfixed of Pyrex 0.9.6.3. There are numerous other bugfixes  
(including several memory leak and refcount fixes) and rdef has been  
renamed to cpdef (its final name).

Special thanks to Stefan Behnel for doing most the hard initial  
merge, and Carl Witty for hunting down a complicated segfault in  
exception handling, and Michael Abshoff for tracking down memory leaks.

- Robert Bradshaw