IPython magics

make encoding setup code safer by not expecting sys.getdefaultencoding() to safely return a bytes object

avoid C compiler warnings for different integer types and signedness when bounds-checking index in obj.pop() optimisation

Expanded POSIX interface

This reverts commit dab5ac36.

Fix typos in the CPython module include file

move file descriptor redirecting to Cython.Utils package and use it as context manager in test runner