refactor(init/wf): use a structure for well_founded (#408)
refactor(init/wf): use a structure for well_founded (#408)

I don't see any reason why this wasn't defined as a structure, and structures generally get better support than one constructor inductives so let's try this and see if anything breaks.



digama0/lean,digama0/lean,fpvandoorn/lean,dselsam/lean,digama0/lean,digama0/lean,leanprover-community/lean,fpvandoorn/lean,fpvandoorn/lean,leanprover-community/lean,leanprover-community/lean,digama0/lean,fpvandoorn/lean,digama0/lean,fpvandoorn/lean,dselsam/lean,leanprover-community/lean,leanprover-community/lean,dselsam/lean,leanprover-community/lean,dselsam/lean,dselsam/lean,fpvandoorn/lean,dselsam/lean