Use draft folder petname if defined

* wl-draft.el (wl-draft-save, wl-draft-reedit,
  wl-draft-buffer-change-number): Use draft folder petname if defined.
* wl-util.el (wl-collect-draft): Use draft folder petname if defined.

Patch provided by Markus Huber in
<mid:2014052108:51:07markus.huber@informatik.uni-augsburg.de>.
Update elmo-file so it works with modern versions of the file utility.

This uses "file -i" instead of "file -m".  Additionally, if file is kind
enough to provide a charset, we trust the result and avoid decoding and
recoding the data multiple times.
Fix typo in elmo-map-folder-list-message-locations (elmo-file-folder).

Due to a missing expand-file-name, we were including subdirectories,
which caused searches to fail.
Merge remote-tracking branch 'ikazuhiro/master'

Conflicts:
	wl/ChangeLog
Signal error if maildir message file is not found

* elmo-maildir.el (elmo-map-message-fetch): Signal error if maildir
  message file is not found.
Make wl-highlight-message use the citation depth for choosing the face.

Rather than using a stateful algorithm for choosing arbitrary but
distinct faces for the various citation prefixes in the message,
this uses the citation depth for plain citations and an arbitrary
hash of the attribution name for SC-style attributions.
Implement draft highlighting using jit-lock-mode.

This uses Emacs' 21 native highlighting mechanism, and is enabled
by default if available.
Don't recompute in-header in wl-draft-default-jit-highlight.

This was wrong, since point may have changed by then, and caused
mis-highlighting of the first line if it was quoted.
Fix parsing of IMAP ALERT replies.