Log Message:
Update roundcube to 1.2.3, including security fix.

pkgsrc changes:
* Drop dependency to pear-Mail_mimeDecode.
* Update dependency.

Other changes:
* Add is_IS, ku_IQ and sq_AL locale support.

RELEASE 1.2.3

* Searching in both contacts and groups when LDAP addressbook with
  group_filters option is used
* Fix vulnerability in handling of mail()'s 5th argument
* Fix To: header encoding in mail sent with mail() method (#5475)
* Fix flickering of header topline in min-mode (#5426)
* Fix bug where folders list would scroll to top when clicking on subscription
  checkbox (#5447)
* Fix decoding of GB2312/GBK text when iconv is not installed (#5448)
* Fix regression where creation of default folders wasn't functioning without
  prefix (#5460)
* Fix bug where deleting folders with subfolders could fail in some cases
  (#5466)
* Fix bug where IMAP password could be exposed via error message (#5472)
* Fix bug where it wasn't possible to store more that 2MB objects in
  memcache/apc, Added memcache_max_allowed_packet and apc_max_allowed_packet
  settings (#5452)
* Fix "Illegal string offset" warning in rcube::log_bug() on PHP 7.1 \ 
(#5508)
* Fix storing "empty" values in rcube_cache/rcube_cache_shared (#5519)
* Fix missing content check when image resize fails on attachment thumbnail
  generation (#5485)
* Fix displaying attached images with wrong Content-Type specified (#5527)