Merge branch 'jk/send-email-mailmap'

"git send-email" learned "--mailmap" option to allow rewriting the
recipient addresses.

* jk/send-email-mailmap:
  send-email: add mailmap support via sendemail.mailmap and --mailmap
  check-mailmap: add options for additional mailmap sources
  check-mailmap: accept "user@host" contacts

diff --cc git-send-email.perl
Simple merge

diff --cc mailmap.c
Simple merge

diff --cc t/t4203-mailmap.sh
Simple merge

diff --cc t/t9001-send-email.sh
Simple merge