RE: Compilation warnings in mouse.el

[Drew Adams]

> Unlike Stefan, I think we should add :group to every defcustom.
> Having them mysteriously missing from some of them is a time bomb:
> remove or add enough defcustoms in the same file, and you have a bug.

100% agreement.  I don't even think we should have introduced this
"shortcut" or "timesaver" feature.  It serves no purpose and can
lead to problems.

> Are there any downsides to having :group in all defcustoms?

Not that I can see.  I'd like to see it be required, but if it's
too late for that then I'd like to see a compiler warning at least.