bpo-38007: Added ts_ prefix to PyType_Spec struct members - #15644

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Without any more context on why this change is needed

@eduardo-elizondo , for the same reason https://bugs.python.org/issue1086854 was opened. The "slots" member causes compilation errors.
Please see https://bugs.python.org/msg350977

To decrease compatibility issues we might rename only the "slots" member.

Unless there is a really good reason to break compatibility (which usually happens when a CPython bug is found), the API shouldn't change.

@eduardo-elizondo , please note that this change does NOT break binary compatibility. Any built library or application which used PyType_Spec and/or its members, will still work correctly, since the memory layout of PyType_Spec remained the same.

If any new version is created for such library/application, usually it is recompiled anyway, then the renaming can be applied in the client code - if those members were in use, at all.
So I don't see any dangerous impact.

Idea about a regression test

So that "slots" or "signals" is not introduced again in the headers as an entity name.

Add a test, which compiles all CPython headers by mimicing Qt headers have included.
Add the -Dslots= -Dsignals= to compiler options.

If there are no compiler errors, the test passes, otherwise fails.

Possible implementation

1. Make a list of the CPython headers.
2. Create a temporary C file with content:

#define slots
#define signals

#include "cpython_header_1.h"
#include "cpython_header_2.h"
...
#include "cpython_header_N.h"

static int something_dummy_so_that_object_file_is_not_empty;

3. Compile it
4. If compiles without error => the test passes, fails otherwise.

I found an "official" Qt solution for this whole issue, the QT_NO_SIGNALS_SLOTS_KEYWORDS and QT_NO_KEYWORDS macros.
See more detail here.

So this PR is not necessary anymore, so I close it.

Cool!