Merge branch 'jn/format-patch-doc' into maint

* jn/format-patch-doc:
  Documentation/format-patch: suggest Toggle Word Wrap add-on for Thunderbird
  Documentation: publicize hints for sending patches with GMail
  Documentation: publicize KMail hints for sending patches inline
  Documentation: hints for sending patches inline with Thunderbird
  Documentation: explain how to check for patch corruption

diff --cc Documentation/git-format-patch.txt
Simple merge