add test for bug #42737.

HEAD didnt have this bug, as it uses a smarter way to iterate over utf-8 chars

ext/pcre/tests/bug42737.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Bug #42737 (preg_split('//u') triggers a E_NOTICE with newlines)
+--FILE--
+<?php
+
+$string = chr(13).chr(10);
+
+$array = preg_split('//u', $string, - 1, PREG_SPLIT_NO_EMPTY);
+
+var_dump(array_map('ord', $array));
+
+?>
+--EXPECT--
+array(2) {
+  [0]=>
+  int(13)
+  [1]=>
+  int(10)
+}