Explicitly initialize tp_print in Python 3.8

When compiling cython-generated extension modules in Python3.8rc1
this error is emitted by the compiler:

  _ext.cpp:8104:1: error: missing initializer for member ‘_typeobject::tp_print’ [-Werror=missing-field-initializers]

The reason is that Python3.8 moved the tp_print slot (d917cfe4051) to
the end of the _typeobject struct and reused the original position for
tp_vectorcall_offset. The current generated code does not initialize the
deprecated tp_print slot that was moved to the end of the struct.

* Handle normalization of unicode identifiers
* Support unicode characters in module names
  (Only valid under Python 3)

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