Cython 0.25 released

[Robert Bradshaw]

I'm happy to announce the release of Cython 0.25 which has numerous
new features and bug fixes. It is available at
https://pypi.python.org/pypi/Cython

We have also moved bug tracking from trac.cython.org to github issues.
However, user support still remains at cython-users@, please refrain
from filing issues until you have confirmed an actual bug.

- Robert


Features added
--------------

* def/cpdef methods of cdef classes benefit from Cython's internal function
  implementation, which enables introspection and line profiling for them.
  Implementation sponsored by Turbostream (www.turbostream-cfd.com).

* The distutils extension ``Cython.Distutils.build_ext`` has now been updated
  to use cythonize which properly handles dependencies.  The old extension can
  still be found in ``Cython.Distutils.old_build_ext`` and is now deprecated.

* Calls to Python functions are faster, following the recent "FastCall"
  optimisations that Victor Stinner implemented for CPython 3.6.
  See https://bugs.python.org/issue27128 and related issues.

* The new METH_FASTCALL calling convention for PyCFunctions is supported
  in CPython 3.6.  See https://bugs.python.org/issue27810

* C++ classes can now have typedef members. STL containers updated with
  value_type.

* Support for bazel using a the pyx_library rule in //Tools:rules.bzl.

* Initial support for using Cython modules in Pyston.  Patch by Daetalus.

* Dynamic Python attributes are allowed on cdef classes if an attribute
  ``cdef dict __dict__`` is declared in the class.  Patch by empyrical.

* Cython implemented C++ classes can make direct calls to base class methods.
  Patch by empyrical.

* New directive ``cython.no_gc`` to fully disable GC for a cdef class.
  Patch by Claudio Freire.

* Buffer variables are no longer excluded from ``locals()``.
  Patch by da-woods.

* Building f-strings is faster, especially when formatting C integers.

* for-loop iteration over "std::string".

* ``libc/math.pxd`` provides ``e`` and ``pi`` as alias constants to simplify
  usage as a drop-in replacement for Python's math module.

* Speed up cython.inline().

* Binary lshift operations with small constant Python integers are faster.

* Some integer operations on Python long objects are faster in Python 2.7.

* Support for the C++ ``typeid`` operator.

Significant Bugs fixed
----------------------

* Division of complex numbers avoids overflow by using Smith's method.

* Some function signatures in ``libc.math`` and ``numpy.pxd`` were incorrect.
  Patch by Michael Seifert.

Other changes
-------------

* The "%%cython" IPython/jupyter magic now defaults to the language level of
  the current jupyter kernel.  The language level can be set explicitly with
  "%%cython -2" or "%%cython -3".