Accept vanilla Linux Foundation signoffs

This allows signing off commits with `git commit -s`

The e-mail regexp is quite loose. I realize a 'real' e-mail check would be too much, but the current form accepts;

`<foo@@@example.com>`, `< @ >`, `<fo o@ex am ple.com>`

Maybe change to `<([^<>@\s]+@[^<>@\s]+)>` (i.e., don't accept white-space, only accept a single `@`)