clean up unicode operator docs
clean up unicode operator docs

- don't mention codepoints; it's not interesting, and it's self-evident
- don't show both the ascii and unicode prototype
- consistently use «» over <<>> when necessary
- merge stub entries for unicode operators with their ascii equivalents
  (where applicable)
- restore o to heading along with ∘

tbrowder/doc,MasterDuke17/doc,tbrowder/doc,MasterDuke17/doc,MasterDuke17/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc