* [Road to C++] Rename ieee754.c.src into ieee754.cpp.src

* [Road to C++] Remove all use of internal template engine

Replace them by regular C++ templates.

* [Road to C++] mv ieee754.cpp.src ro ieee754.cpp

Clang-format it, and update build system accordingly.

* Fix 'unnecessary parentheses in declaration of ‘__NPY_UNUSED_TAGGEDc’ [-Wparentheses]'

* [Road to C++] Fix misc conversion issues in ieee754.cpp

- hex float literal are not supported in C++
- avoid overload issues when numpy_longdouble ultimately is equal to double
- _statusfp2 exepcts unsigned arguments

LooseVersion is provided by Python distutils, which is going away in
3.12. This PR vendors _pep440 from scipy and uses it as a replacement.
Numpy distutils is not touched, replacing LooseVersion in that package
was considered too risky, and numpy distutils will need to go away when
Python distutils does.

NumPy may fail to build with the default vendored distutils in
setuptools>=60. Rather than panic and die when new setuptools is found,
let's check (or set, if possible) the SETUPTOOLS_USE_DISTUTILS
environment variable that restores "proper" setuptools behavior.

ENH: add hook and test for PyInstaller.

Adding this special hook file tells PyInstaller what files a self contained
NumPy application needs to run. A test is included to verify that the hook still
finds all necessary files.

Closes #17184.

NumPy does not build with setuptools versions greater than '60.0.0'.
Check the version when setuptools is imported in setup.py and raise
a RuntimeError if the version is too recent. That way we avoid people
opening issues when their build fails for that reason.

Closes #20692.

[ci skip]

Previously, this was not strictly enforced for the only purpose of
running LGTM (hoping it would be fixed before the 1.22 release).

Co-authored-by: Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>

When Git is not installed, it is possible to get useless version strings
from versioneer, such as `0+unknown`.  Give a more informative error in
that case.

This is just a technical prototype to measure and discuss the impact and
implication of moving to C++ for kernel code generation.

This fixes setup.py to correctly detect the release status and base
version from the full version string provided by versioneer. Before
this fix, versions like '1.22.0.dev0+...' were correctly handled,
but versions like '1.21.0rc1+...' were not.

When creating the `bad_commands` dictionary it is useless to declare commands that are already set with a default message in the 329th line's for loop

This issue came in because of commit 9b3f650 a month ago.
`bdist_egg` has always been missing from the command list, but
that wasn't a problem because missing commands were simply
ignored by the validation. After that commit we started raising
a RuntimeError instead.

MAINT: Add dist_info to "other" setup.py commands.

The follwing changes are made to 'setup.py'.

- Add 'dist_info' to the valid 'setup.py' commands. The 'dist_info'
  command was added to setuptools in 2017 and we were following the
  unrecognized command path in setup.py which raised a warning.
- Add 'version' to the recognized information commands, it came in with
  the move to versioneer.
- Include the arguments passed to 'setup.py' when the unrecognized
  command warning is raised. This will aid in maintaining the command
  checks in the future.

Before this change, it would give a random syntax error somewhere
in `versioneer`.

If sdist uses setuptools there can be problems, see gh-7127.

The new tags look like '1.21.0.dev0+98.gaa0453721f', where '98' is the
number of commits since the 1.21.0 branch was started and 'aa0453721f'.
The chosen form may be specified in the 'setup.cfg' file. This PR adds
two new files 'numpy/_version.py' and 'numpy/version.py'. The latter
is kept because it is part of the public API and is actually used by
some downstream projects, but it is no longer dynamically created.

See https://github.com/python-versioneer/python-versioneer/ for more
information.

We missed a few first time around.

This adds a timestamp to development versions of NumPy. We used to do
this for NumPy nightly builds so that pip would pickup the latest
version, but pip 20.3 breaks with that as there is disagreement between
the wheel name and the internal version.

Closes #17885.

- Update setup.py
- Update pavement.py
- Add 1.21.0-note.rst
- Update npyconfig.h
- Clear release/upcoming_changes

Closes gh-17702

ENH: Add `Typing :: Typed` to the PyPi classifier

Co-authored-by: Eric Wieser <wieser.eric@gmail.com>