PHP-Intl: fix up system check grammar and add pre-upgrade message.

CRM/Upgrade/Incremental/php/FiveTwentySeven.php

@@ -29,6 +29,10 @@ class CRM_Upgrade_Incremental_php_FiveTwentySeven extends CRM_Upgrade_Incrementa
     // if ($rev == '5.12.34') {
     //   $preUpgradeMessage .= '<p>' . ts('A new permission, "%1", has been added. This permission is now used to control access to the Manage Tags screen.', array(1 => ts('manage tags'))) . '</p>';
     // }
+    $preUpgradeMessage .= '<p>' . ts('Starting with version 5.28.0, CiviCRM will
+      require the PHP Internationalization extension (PHP-Intl).  In preparation
+      for this, the system check will show a warning beginning in 5.27.0 if your
+      site lacks this extension.') . '</p>';
   }
 
   /**

CRM/Utils/Check/Component/Env.php

@@ -991,7 +991,7 @@ class CRM_Utils_Check_Component_Env extends CRM_Utils_Check_Component {
     if (!extension_loaded('intl')) {
       $messages[] = new CRM_Utils_Check_Message(
         __FUNCTION__,
-        ts('This system currently does not have the PHP-INTL extension enabled please contact your system administrator about getting the extension enabled'),
+        ts('This system currently does not have the PHP-Intl extension enabled.  Please contact your system administrator about getting the extension enabled.'),
         ts('Missing PHP Extension: INTL'),
         \Psr\Log\LogLevel::WARNING,
         'fa-server'