When compiling to C++ code and using automatic conversion from Python
str to C++ string, Cython inserts this function template but generates the warning:
warning: string.from_py:15:63: local variable 'length' might be referenced before assignment

Minor cleanup regarding __Pyx_PyMethod_New

Make sure to include "Python.h" also from the "public" header file, which depends on its declarations.
Closes #3133.

Remove duplicated line from __Pyx_c_pow

When compiling to C++ code and using automatic conversion from Python
str to C++ string, Cython inserts this function template but generates the warning:
warning: string.from_py:15:63: local variable 'length' might be referenced before assignment

* Special-case setting __new__ in class

* Always bind Cython functions

* TEST: add cgetter test for pointer and pxd use
* BUG: handle more AttributeNode-with-property-decorator
* BUG: fix numpy/__init__.pxd
* ENH: add @property for ndarray.size, formatting cleanup

Add an assertion for the assumption that all identifier start characters are also valid continuation characters, so that we notice it if that ever changes.