To be used in https://github.com/cython/cython/pull/4241

See https://github.com/cython/cython/pull/3626

Closes https://github.com/cython/cython/issues/4172

Allowing these gives people the false impression that they do something meaningful.

Closes https://github.com/cython/cython/issues/887
Closes https://github.com/cython/cython/issues/3959

People often have unrealistic expectations about what this typing helps with, so I've added a small paragraph to try to make it clearer.

The directives are called `optimize` rather than `optimization`.

1) Entry utility_code wasn't being imported unless the entry was visibly used. The utility code is needed for the definition even if unused. I think this is what utility_code_definition is for, but I'm not completely sure. I also had to add some calls to ensure it's used.

2) CppOptionalTempCoercions weren't being moved correctly. Tested by printing from the destructor.

3) cdef-class attributes weren't being created or destroyed correctly. Tested by printing from the destructor

See https://github.com/cython/cython/issues/4022#issuecomment-870394893

This avoids the need for default constructors of stack allocated variables and temps by allowing late initialisation.

Closes https://github.com/cython/cython/issues/4160

Add missing argument when instantiating a test class. The argument was added in https://github.com/cython/cython/commit/3bd321f17474aafde1bd497163b3e7ba089ee2cc

Fixes https://github.com/cython/cython/issues/4243
(and probably a bunch more annotation bugs)

AnnotationNode doesn't have any child_attrs/subexprs because it mostly doesn't want to be analyzed (it's just transformed to an evaluable string). However this means that InterpretCompilerDirectives wasn't visiting its children to set is_cython_module and so the typing was failing. I've special-cased InterpretCompilerDirectives to visit AnnotationNode fully.

Fixes https://github.com/cython/cython/issues/4198
Fixes https://github.com/cython/cython/issues/4196

This was causing a (correct) warning.

It looks like putting the title between `.. glossary::` and the entries messed it up.

Fixes issue https://github.com/cython/cython/issues/3065
Fixes issue https://github.com/cython/cython/issues/3066

* delete cpp_exception_declaration_compatibility test
  Because I'm emitting an error at an earlier stage I don't think there's a way to get this test to work.

Reported in https://github.com/cython/cython/pull/4228

Closes https://github.com/cython/cython/issues/3922

Partially reverts https://github.com/cython/cython/commit/1027db04fb7c5bbfea2b9bcdfce0b1f384e26a93

Also make a couple of improvements regarding clarity and text formatting.

See https://github.com/cython/cython/issues/4187

* .gitignore: add directory for docs build and cython_debug
* doc-requirements.txt: add sphinx-tabs
* conf.py: add and setup sphinx-tabs extension
* Create _static\css\tabs.css for customisation
* add "two-syntax-variants-used" file as a preface about the different typing variants