The types of variables __pyx_PickleError, __pyx_result from generated
unpickle function, and variables state, _dict from __reduce_cython__
generated method were not declared.
So warnings were raised with warn.undeclared for every single extension
type.

Now, we define the type of these variables, and no warnings are raised.

Fix Memviewslice docstrings & Test

[#2634] Merge Fix 

Workaround for long internals misconfiguration on 64-bit MinGW.

Also add a compile time check for SIZEOF_VOID_P.

This fixes #2670.

See also
https://bugs.python.org/issue35037
https://bugs.python.org/issue4709

Fix reimport_from_subinterpreter test when PYTHONPATH is set

Correct the handling of line tracing errors on try-statements. Previously, this jumped to the error label of the try-statement, whereas it must target the outer error label instead.
Closes #2274.

Only error out for non-ASCII literals on actual bytes literals

Smarter bounds checks

See https://bugs.python.org/issue28397

Add --3str command line option to 'cython' program

Improve message for deprecated "language=..." option

Fixes #2634

Rename the options of the "check_size" feature to make them more obvious: "warn" warns, "error" fails, and "extend" silently allows extending.
Closes #2627.

Enable "check_size=False" for the NumPy ndarray and dtype extension types to avoid warning about otherwise backwards compatible changes.