API: Fix structured dtype cast-safety, promotion, and comparison

This PR replaces the old gh-15509 implementing proper type promotion
for structured voids.  It further fixes the casting safety to consider
casts with equivalent field number and matching order as "safe"
and if the names, titles, and offsets match as "equiv".

The change perculates into the void comparison, and since it fixes
the order, it removes the current FutureWarning there as well.

This addresses https://github.com/liberfa/pyerfa/issues/77
and replaces gh-15509 (the implementation has changed too much).

Fixes gh-15494  (and probably a few more)

Co-authored-by: Allan Haldane <allan.haldane@gmail.com>

0 files changed, 0 insertions, 0 deletions