lib: Upgrade php-gettext from 1.0.11 to 1.0.12

https://launchpad.net/php-gettext

The local change to rename the gettext_reader function to
__construct (commit 00b6b66827) has been
preserved.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

lib/gettext/gettext.php

@@ -350,6 +350,10 @@ class gettext_reader {
    * @return int array index of the right plural form
    */
   function select_string($n) {
+    if (!is_int($n)) {
+      throw new InvalidArgumentException(
+        "Select_string only accepts integers: " . $n);
+    }
     $string = $this->get_plural_forms();
     $string = str_replace('nplurals',"\$total",$string);
     $string = str_replace("n",$n,$string);