* Use the same fallback as for missing PEP-393 support.
* Prepare for "PyUnicode_READY()" and "PyUnicode_WCHAR_KIND" to be removed in Py3.12.
  See https://www.python.org/dev/peps/pep-0623/
* Avoid C compiler warnings about deprecated C-API functions in Py3.9+.

Closes https://github.com/cython/cython/issues/3925

* Use the same fallback as for missing PEP-393 support.
* Prepare for "PyUnicode_READY()" and "PyUnicode_WCHAR_KIND" to be removed in Py3.12.
  See https://www.python.org/dev/peps/pep-0623/
* Avoid C compiler warnings about deprecated C-API functions in Py3.9+.

Closes https://github.com/cython/cython/issues/3925

This change introduced Python object statics, which has a negative impact on multiple interpreter support etc.

This reverts commit b68f2585.

Hard-disable the MergeVTables() step during the extension type setup when using the Limited API. There might be a way to make it work, but it currently won't.

Also see https://github.com/cython/cython/pull/4107

Allow searching for include/import files without passing a source pos tuple and clean up the call chains a little.

For reasons I don't full understand, including "windows.h" seems to break everything. There's an alternative sleep function in stdlib.h so I've used that instead since it makes the point just as well.

Disable __Pyx_PyType_Ready() usage in PyPy & friends where it fails to compile currently. They should generally be happy with their own implementation.
See https://github.com/cython/cython/pull/4107

Allow inheriting from cimported multiply inherited class.

Fix Python install script on appveyor: The URL path uses three digit Python versions, not just major.minor.

According to the docs, "/Od" is the default in MSVC, so in order to get it, it should be enough to clear CFLAGS.
Setting it generates warnings in Py3.9 on appveyor ("source file '"/Od"' ignored"), suggesting that the option is not recognised as such.
https://docs.microsoft.com/en-us/cpp/build/reference/od-disable-debug?view=msvc-160

Remove "PYTHONHOME" setting from embed-test since it seems to break the I/O encoding setup in (at least) Py3.8+ venvs.

Signed-off-by: Andrew V. Jones <andrew.jones@vector.com>

Closes https://github.com/cython/cython/pull/4101
See https://github.com/cython/cython/issues/4100

* Handle constant folding for LanguageLevel 2 on Python 3. Ensure that when StrNode is a BytesLiteral, that we don't coerce it to unicode.
* Add test for string multiplication bug. Needed to change the TreePath slightly to allow bytes-to-str comparison.

Fixes https://github.com/cython/cython/issues/3951

Remove incorrect dict unpacking optimisation that leaked external dict changes into the result (GH-4091)

Closes https://github.com/cython/cython/issues/3227

* Disable GC-sensitive NumPy tests on PyPy
* Removed @testcase decorator pattern that was causing tests to be run twice