Merge pull request #484 from renaudallard/master

Allow keyfiles readable by group to enable key sharing between services
remove comma that shouldn't be there

reported by Alexander Hall
Merge branch 'master' of https://github.com/OpenSMTPD/OpenSMTPD
Merge pull request #487 from renaudallard/master

Introduces "limit session" keywords to replace fixed values
Add note for wiki and correct Arch Linux
Merge pull request #488 from svenstaro/patch-1

Add note for wiki and correct Arch Linux