gh-123681: Check NORMALIZE_CENTURY behavior at runtime; require C99 (GH-136022)

A runtime check is needed to support cross-compiling.

Remove the _Py_NORMALIZE_CENTURY macro.
Remove _pydatetime.py's _can_support_c99.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Petr Viktorin committed 7mo ago

719e5c3f7111bcda5eee72fe648786c427c4d4c2

Parent: b07a267

Committed by GitHub <noreply@github.com> on 8/19/2025, 10:59:03 AM