[Cython] Speed up cython for enum declarations

[Stefan Behnel]

Robert Bradshaw wrote:
> Unfortunately the devel branch is even less stable than usual, as
> temporary variable handling is undergoing a major shift

"less stable" is a clear understatement. I actually consider it broken in
a couple of places. A lot of code will still work, but crashes (both
compiler crashes and runtime crashes) should be expected.

Stefan