Pull more documentation updates from Jon Corbet:
 "A few more documentation patches that wandered in and have no reason
  to wait; these include some improvements to the suggestions for email
  clients and patch submission"

* tag '4.4-additional' of git://git.lwn.net/linux:
  Documentation: Add minimal Mutt config for using Gmail
  Documentation: Add note on sending files directly with Mutt
  Documentation: dontdiff: remove media from dontdiff
  Documentation/SubmittingPatches: discuss In-Reply-To
  Remove email address from Documentation/filesystems/overlayfs.txt
  can-doc: Add missing semicolon to example