This should complete #3171 in silencing -Wmissing-field-initializers.

* IPython magic: hide internal traceback when compilation fails
* IPython magic: hide internal traceback when build fails

Also fix tests in libcpp_algo (how did this ever work?)

Closes GH-1462.

* Rearrange libcpp.algorithm to match cppreference and reformat
* Add all_of, any_of and none_of to libcpp.algorithm
* Add count and count_if to libcpp.algorithm
* Add string(first, last) constructor to libcpp.string
* Add the simplest overload of mismatch to libcpp.algorithm
* Add find, find_if, and find_if_not to libcpp.algorithm
* Add find_end to libcpp.algorithm and distance to libcpp.iterator
* Add find_first_of to libcpp.algorithm
* Add adjacent_find to libcpp.algorithm
* Add search to libcpp.algorithm
* Add search_n to libcpp.algorithm
* Add exception specifiers in libcpp.algorithm
* Add predicated overload of find_end, search and search_n to libcpp.algorithm

This is more follow up to https://bugs.python.org/issue37250

The action taken is:
 - restore tp_print to not break all of the sdists on pypi for py38
 - remove tp_print for real in py39

In https://github.com/cython/cython/pull/3171 tp_print was initialized
for PY_VERSION_HEX >= 0x030800b4 however, when trying to use cython
with cpython master (aka py39) there are compile time exceptions due
to too many initializers:

   error: too many initializers for ‘PyTypeObject’ {aka ‘_typeobject’}

This fixes that by putting an upper bound on the ifdef of including
pt_print at the end of the object.

This is more follow up to https://bugs.python.org/issue37250

The action taken is:
 - restore tp_print to not break all of the sdists on pypi for py38
 - remove tp_print for real in py39

In https://github.com/cython/cython/pull/3171 tp_print was initialized
for PY_VERSION_HEX >= 0x030800b4 however, when trying to use cython
with cpython master (aka py39) there are compile time exceptions due
to too many initializers:

   error: too many initializers for ‘PyTypeObject’ {aka ‘_typeobject’}

This fixes that by putting an upper bound on the ifdef of including
pt_print at the end of the object.

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

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.

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