Add support for no-op translations

refs #5600

library/Icinga/Application/functions.php

@@ -3,6 +3,23 @@
 
 use Icinga\Util\Translator;
 
+
+/**
+ * No-op translate
+ *
+ * Supposed to be used for marking a string as available for translation without actually translating it immediately.
+ * The returned string is the one given in the input. This does only work with the standard gettext macros t() and mt().
+ *
+ * @param   string  $messageId
+ *
+ * @return  string
+ */
+function N_($messageId)
+{
+    return $messageId;
+}
+
+
 if (extension_loaded('gettext')) {
 
     /**

modules/translation/library/Translation/Util/GettextTranslationHelper.php

@@ -290,6 +290,7 @@ class GettextTranslationHelper
                     '--keyword=t:1,2c',
                     '--keyword=tp:1,2',
                     '--keyword=tp:1,2,4c',
+                    '--keyword=N_',
                     '--sort-output',
                     '--force-po',
                     '--omit-header',