Fix fatal errors on systems without mbstring extension or mb_regex_encoding() function (#1490280)

CHANGELOG

@@ -10,6 +10,7 @@ CHANGELOG Roundcube Webmail
 - Fix handling of some improper constructs in format=flowed text as per the RFC3676[4.5] (#1490284)
 - Fix performance of rcube_db_mysql::get_variable()
 - Fix missing or not up-to-date CATEGORIES entry in vCard export (#1490277)
+- Fix fatal errors on systems without mbstring extension or mb_regex_encoding() function (#1490280)
 
 RELEASE 1.1.0
 -------------

program/include/iniset.php

@@ -68,11 +68,14 @@ spl_autoload_register('rcmail_autoload');
 // backward compatybility (to be removed)
 require_once INSTALL_PATH . 'program/include/bc.php';
 
-// load the UTF-8 portablity layer from Patchwork
-if (!function_exists('iconv') || !function_exists('utf8_encode') || !extension_loaded('mbstring')) {
-    \Patchwork\Utf8\Bootup::initAll();
+// load the UTF-8 portability layers from Patchwork
+// don't load mbstring layer as it conflicts with Roundcube Framework (#1490280)
+if (!function_exists('iconv')) {
+    \Patchwork\Utf8\Bootup::initIconv();
+}
+if (!function_exists('utf8_encode')) {
+    \Patchwork\Utf8\Bootup::initUtf8Encode();
 }
-
 
 /**
  * PHP5 autoloader routine for dynamic class loading

program/lib/Roundcube/bootstrap.php

@@ -78,9 +78,11 @@ if (!defined('RCUBE_LOCALIZATION_DIR')) {
 }
 
 // set internal encoding for mbstring extension
-if (extension_loaded('mbstring')) {
+if (function_exists('mb_internal_encoding')) {
     mb_internal_encoding(RCUBE_CHARSET);
-    @mb_regex_encoding(RCUBE_CHARSET);
+}
+if (function_exists('mb_regex_encoding')) {
+    mb_regex_encoding(RCUBE_CHARSET);
 }
 
 // make sure the Roundcube lib directory is in the include_path