[PHP] Add support for PHP7.

PHP5's C extension API has changed substantially so you need to use
-php7 to specify you want PHP7 compatible wrappers.
Fixes https://github.com/swig/swig/issues/571

Examples/test-suite/php5/arrayptr_runme.php

@@ -0,0 +1,14 @@
+<?php
+
+require "tests.php";
+require "arrayptr.php";
+
+// No new functions
+check::functions(array(foo));
+// No new classes
+check::classes(array());
+// now new vars
+check::globals(array());
+
+check::done();
+?>