Closes #2514.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/gen.html).

Closes #2514.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/gen.html).

PySlice_Unpack() and PySlice_AdjustIndices() were missing from
slice.pxd.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/slice.html).

PySlice_Unpack() and PySlice_AdjustIndices() were missing from
slice.pxd.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/slice.html).

Closes GH-3418.

Original change https://github.com/cython/cython/pull/1927

Exclude failing "complex.h" test on Windows, where old MSVC versions lack "<complex.h>" entirely and more recent versions fail to compile the test.

Reasoning being that this make it easier to catch pypy3
regressions as they happen.

* Fixed some very simple pypy3 failures (largely to do with
  different exception strings)
* Splits pypy3_bugs.txt into three files
  - one for bugs that cause hard crashes (which we don't want to
    run in Travis at all);
  - one for bugs that are probably unfixable because they're just
    due to implementation details (e.g. when destructors are
    called).
  - all other bugs remain in pypy3_bugs.txt
  (The categorization has been done fairly quickly, so some bugs
  may be in the wrong place)
* Made sure (hopefully) all bugs are now categorized, so a basic
  runtests.py with pypy3 should hopefully pass
* Changed pypy3 to be required in Travis
* Added an extra (optional) test that runs through pypy3_bugs.txt.
  The majority of this is expected to fail. This requires an
  extra option to runtest.py "--listfile", which just runs through
  the tests listed in the file.

I haven't made pypy2 a required test in this commit - since Python2 support is deprecated soon, there seemed limited value in putting much effort into pypy2.

Added faulthandler to runtests in the hope of being able to pin-down segmentation faults better on Travis

FileListExcluder matches regexes, not just name. Uses the same mechanism as is used for processing string passed on commandline

* Work around a C compiler warning (in PyPy's cpyext).
* Avoid a C compiler warning in PyPy3.
* Fix a C compiler warning about an unused variable when compiling in PyPy.

Closes #2643.

PyNumber_MatrixMultiply() and PyNumber_InPlaceMatrixMultiply() were
missing from number.pxd.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/number.html).

PyNumber_MatrixMultiply() and PyNumber_InPlaceMatrixMultiply() were
missing from number.pxd.

The comments are taken from the C API documentation
(https://docs.python.org/3.8/c-api/number.html).

Fixes "Make it a bit less likely that the Python version of cython.cast() does something unexpected/wrong."

Strings werren't static for the limited API so had to be set at module init rather than compile time.

* Fixed issue where fused functions didn't register as cyfunctions

Issue https://github.com/cython/cython/issues/3384

This happened where Cython was using a shared API because the
CyFunction type imported from the shared api wasn't the same as
used to initialize the fused function tp_base.

* Fixed issue where fused functions didn't register as cyfunctions

Issue https://github.com/cython/cython/issues/3384

This happened where Cython was using a shared API because the
CyFunction type imported from the shared api wasn't the same as
used to initialize the fused function tp_base.