Merge branch 'en/fast-import-looser-date'

Some repositories in the wild have commits that record nonsense
committer timezone (e.g. rails.git); "git fast-import" learned an
option to pass these nonsense timestamps intact to allow recreating
existing repositories as-is.

* en/fast-import-looser-date:
  fast-import: add new --date-format=raw-permissive format

diff --cc Documentation/git-fast-import.txt
Simple merge

diff --cc fast-import.c
Simple merge

diff --cc t/t9300-fast-import.sh
Simple merge