Fix warnings in PHP7 in gettext library

Not sure how to commit this upstream, the library seems to be
unmaintained.

inc/lib/gettext/gettext.php

@@ -98,7 +98,7 @@ class gettext_reader {
    * @param object Reader the StreamReader object
    * @param boolean enable_cache Enable or disable caching of strings (default on)
    */
-  function gettext_reader($Reader, $enable_cache = true) {
+  function __construct($Reader, $enable_cache = true) {
     // If there isn't a StreamReader, turn on short circuit mode.
     if (! $Reader || isset($Reader->error) ) {
       $this->short_circuit = true;
@@ -129,6 +129,9 @@ class gettext_reader {
     $this->originals = $this->readint();
     $this->translations = $this->readint();
   }
+  function gettext_reader($Reader, $enable_cache = true) {
+    self::__construct($Reader, $enable_cache);
+  }
 
   /**
    * Loads the translation tables from the MO file into the cache