Avoid calling "PyErr_Clear()" in "__Pyx_CyFunction_get_is_coroutine()" if no error was raised (by our code).

* Avoid UtilityCode from cimport_from_pyx files
* Unique names for generated cfunc wrappers, avoid pxd pickle code
* Set .in_pxd on nodes prior to analyse_declarations

Fixes #3716
Fixes #3741
Fixes #3734

Mostly with the hope that the tests pass. Ideally we should support the most recent version.

Closes https://github.com/cython/cython/issues/2233

Even though the Python documentation states, that PyUnicode_KIND will return an int,
it actually returns a value of the underlying type of the PyUnicode_Kind enum.
This could be e.g. an unsigned int which can cause warnings about signed/unsigned comparisons.

Backported from 3dc2b9df
Partial fix for https://github.com/cython/cython/issues/3919

clang warns about dead code when an if-statement always evaluates to false. This warning can be silenced using an extra '()'.

The `test.support` has been split into sub-modules. Adapt `test_exceptions` (originally coped from CPython) for these changes.

Eliminate C compiler warnings by making the constness of the
char* pointers in the declarations in pycapsule.pxd match
the actual types of the PyCapsule_* functions.

Disable time_pxd test in Python 3.4

It uses features that are unavailable thus always fails

Test was introduced in https://github.com/cython/cython/pull/3767

Closes https://github.com/cython/cython/issues/4000

Closes https://github.com/cython/cython/issues/4000

It was broken in https://github.com/cython/cython/pull/3976 which added an additional error message.

Fixed e_decorators test

Warning message on cpdef variables (0.29.x)

Expose "long and overflow" cpython functions

These functions are available since Python 2.7.

Close #3980

Changed "declared after use" warning to error

* ENH: implement cpython/time.pxd
Co-authored-by: scoder <stefan_ml@behnel.de>

In 0.11.1 is was marked as an warning that would become an error.
3.0 is probably either the time to make it an error (or to remove
the note that it'll be an error in future)