Call load_host_config() and add reference to Howto_Config (#1485040)

config/main.inc.php.dist

@@ -273,6 +273,7 @@ $rcmail_config['address_book_type'] = 'sql';
 $rcmail_config['dont_override'] = array();
 
 // try to load host-specific configuration
+// see http://trac.roundcube.net/wiki/Howto_Config for more details
 $rcmail_config['include_host_config'] = false;
 
 // don't let users set pagesize to more than this value if set

program/include/rcube_config.php

@@ -54,6 +54,9 @@ class rcube_config
     // load database config
     include_once(INSTALL_PATH . 'config/db.inc.php');
     $this->prop += (array)$rcmail_config;
+    
+    // load host-specific configuration
+    $this->load_host_config();
 
     // fix paths
     $this->prop['skin_path'] = $this->prop['skin_path'] ? unslashify($this->prop['skin_path']) : 'skins/default';