Requires-clause — updated

The previous post, “Requires-clause”, contained incorrect information about parentheses inside a requires-clause. Token || inside parentheses is still interpretted as a disjunction of two constraints. I apologize for misleading the readers. I also want to thank James Pfeffer for bringing this error to my attention. The post has now been corrected. You might wish to re-read section Conjunction and Disjunction.