Change the elmo-folder-synchronize use of MASK

Use the MASK argument, if supplied, to compare against the list of
messages in the msgdb to determine which messages need to be
synchronized.
Merge pull request #79 from egh/feature/use_mask

Change the elmo-folder-synchronize use of MASK
Add ChangeLog entry.
elmo-multi.el (elmo-folder-search): Rewritten.  Avoid redundant use of elmo-folder-list-messages.
Remove elmo-list-difference.
fix transparency of XPM for GNU Emacs (#26)
elmo-split.el (elmo-split-subr): Fix typo.
elmo-imap4.el (elmo-imap4-elist): Fix typo.
Refine elmo-nntp-read-response and elmo-pop3-read-response.
Optimize interactive folder search.
elmo-pop3.el (elmo-pop3-auth-apop, elmo-folder-status): Fix typo of regexp.
Merge pull request #80 from egh/feature/fix_transparency

fix transparency of XPM for GNU Emacs (#26)
set encoding for wl-ja.texi
Merge pull request #81 from egh/feature/set_texi_encoding

set encoding for wl-ja.texi
Add ChangeLog entries.
Fix error running timer `wl-biff-event-handler'

Cf. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=768910
Merge pull request #84 from tats/bug/idle-timer

Fix error running timer `wl-biff-event-handler'
Correct argument of run-with-idle-timer for wl-biff

Cf. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=768910
Indentation fix
Correct arguments of idle timer for wl-save-drafts