* 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.

Default arguments are now copied when the bound fused function is created.

Default arguments are now copied when the bound fused function is created.

1. DefNode.has_fused_arguments was set too early (before
locals/annotations) were evalutated, so function was not treated
as fused.
2. When re-evaluating the specializations of the fused function
it was treated as a redefinition because the locals/annotation was
reapplied over the specialized type.
3. Including annotation as string (required changes to
StringNode.analyse_as_type), and extra tests for fused type defined
as cython.fused_type in the Py file

Closes #3331.

Closes #1427 

Closes #3331.

* Cleanup of string initialization code for limited API

Now appears in a few large blocks rather than

```
 # if CYTHON_LIMITED_API
   individual string line
 # endif
```

* Fixed issue with some unicode strings, e.g.

```
# cython: language_level=3str, binding=True

def non_ascii_str():
    s = 'ø\x20\u0020'
    assert isinstance(s, str)
    return s
```

"@subsitute: tempita" tag ensures that they are loaded in tempita utility code class

Use correct "Py_mp_subscript" type slot for getitem() method instead of "Py_mp_ass_subscript" (which is for assignments).

Fix "unused" C compiler warning for "__pyx_FusedFunction_mapping_methods" when using the limited C-API.

* omp declare privates on outer loop, since inner loops are not 'omp parallel for'ified

They'd generate two calls - one exception checked and one not

They'd generate two calls - one exception checked and one not

Avoid deprecation warning in Cython-Inline by setting the default language level to "3str" if none is provided.

* Add more limited api support
* Fix Fused Functions
* Fixed profile
* Use PyModule_GetDict
* Simplify __Pyx_Globals
* Address issues in CommonStructures
* ifdef guard CyFunction and FusedFunction

See #2686.

Close #2686.

* omp declare privates on outer loop, since inner loops are not 'omp parallel for'ified

* Changed always_allow_keywords_T295 for Py3.9

https://bugs.python.org/issue37645 appears to change some error
messages slightly (including the qualname and not just the
function name). This change just allows doctest to cope with
both the new and old messages