Implement the warning for typeclass instances without an explicit locality.
Implement the warning for typeclass instances without an explicit locality.

This allows to follow the same transition path as mere hints.

SkySkimmer/coq,Zimmi48/coq,Zimmi48/coq,SkySkimmer/coq,JasonGross/coq,coq/coq,coq/coq,JasonGross/coq,Zimmi48/coq,coq/coq,ejgallego/coq,Zimmi48/coq,JasonGross/coq,ejgallego/coq,ejgallego/coq,JasonGross/coq,ejgallego/coq,SkySkimmer/coq,SkySkimmer/coq,coq/coq