[3.14] gh-135755: Make Py_TAIL_CALL_INTERP macro private (#138981)

[vstinner]

Rename Py_TAIL_CALL_INTERP to _Py_TAIL_CALL_INTERP.

(cherry picked from commit 6504f20)

• Issue: Undocumented 3.14 C API #135755

[vstinner]

@Fidget-Spinner@corona10@hugovk: Does it sound reasonable to you to make this macro private in 3.14? Sorry, it's a very late change in 3.14.

I would be fine with rejecting this PR and leaving the macro as it is in 3.14.

[corona10]

lgtm, I think that it is safe to be merged at 3.14, but it's upto @hugovk want or not :)

[itamaro]

lgtm, I think that it is safe to be merged at 3.14, but it's upto @hugovk want or not :)

Define "safe" ;)
It will require us to change how we're building 3.14 internally to avoid losing tail call interpreter.
Admittedly, our build is pretty far from "standard", and the adjustment would be trivial, but if we miss this change and don't adapt how we build, tail call interpreter would be silently turned off and it could be hard to notice, which would be unfortunate.

[vstinner]

You don't use the configure option to enable the optimization?

[itamaro]

No, we don't run configure when building with buck2

[hugovk]

I think this is too late for 3.14.

[vstinner]

I think this is too late for 3.14.

Sure, I'm fine with this decision.