Use _ind and _rec for eliminators, close #517
oops, add Types/Nat
global unset elimination schemes
actually, we want Local Unset Elimination Schemes
define Empty_rect
elimination schemes for sig
Local Unset Elimination Schemes in Overture, with documentation
missing Local in Bool
comments about Coq bug 3745
Merge pull request #577 from mikeshulman/indrec

Use _ind and _rec for eliminators, close #517