Log Message:
Update to 0.18:

0.18 (2013-01-28)
=================

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

* Named Unicode escapes ("\N{...}") are supported.

* Python functions/classes provide the special attribute "__qualname__"
  as defined by PEP 3155.

* Added a directive ``overflowcheck`` which raises an OverflowException when
  arithmetic with C ints overflow.  This has a modest performance penalty, but
  is much faster than using Python ints.

* Calls to nested Python functions are resolved at compile time.

* Type inference works across nested functions.

* ``py_bytes_string.decode(...)`` is optimised.

* C ``const`` declarations are supported in the language.

Bugs fixed
----------

* Automatic C++ exception mapping didn't work in nogil functions (only in
  "with nogil" blocks).