How upgrade roundcubemail?

==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.2
- Linux/BSD distribution name and version: Centos 6.6
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? NO
- Related log if you're reporting an issue:
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How upgrade roundcubemail to v1.1.2?