/**
 * Enable this constant if you want to send your email
 * through the smarty templating engine (allows you to do 
 * conditional and more complex logic)
 **/
if (!defined('CIVICRM_MAIL_SMARTY')) {
  define( 'CIVICRM_MAIL_SMARTY', 1 );
}

In addition, you should disable entities in CK editor. You can do that at Administer->Customize Data & Screens->Display Preferences. Then scroll down and click the “Configure CKEditor” button.

On the subsequent page, you will need to set entities to false.

1. ssh to server
2. ensure everything is backed up right now, not last night. This is normally handled automatically on a daily basis by ManageWP and also by a local msqldump process.
3. Disable CiviCRM logging because of DB upgrade issues. Administer->System Settings->Misc
4. Disable InnoDB full text search because of DB upgrade issues. Administer->Customize Data->Search Prefs
5. cd to /var/www
6. visit https://civicrm.org/download in a browser and get the download links
7. download civicrm-….zip (and if needed, the localisation files.tar.gz) to somewhere convenient using wget
8. cd to wp-content/plugins directory of site
9. mv civicrm directory to /var/www/sitename/civicrm.bak (This is to backup what we have just in case of trouble and to get the existing one out of the way for the new code.)
10. unzip civicrm-….zip to plugins directory
11. IF NEEDED: cd to civicrm directory and tar xvzf civicrm…_l10n.tar.gz
12. cd to wp-content/uploads/civicrm/templates_c and delete everything inside templates_c
13. upgrade the database by visiting /wp-admin/admin.php?page=CiviCRM&q=civicrm/upgrade&reset=1
14. re-enable logging if needed
15. re-enable InnoDB full text search if needed
16. may need to www-unlock and www-lockdown once or twice to correct permissions.
17. confirm site function
    1. test a contribution form
    2. test a mailing
    3. test public pages