[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/director_stl_runme.php

@@ -0,0 +1,60 @@
+<?php
+
+require "tests.php";
+require "director_stl.php";
+
+// No new functions
+check::functions(array(foo_bar,foo_ping,foo_pong,foo_tping,foo_tpong,foo_pident,foo_vident,foo_vsecond,foo_tpident,foo_tvident,foo_tvsecond,foo_vidents,foo_tvidents));
+// No new classes
+check::classes(array(Foo));
+// now new vars
+check::globals(array());
+
+class MyFoo extends Foo {
+  function ping($s) {
+    return "MyFoo::ping():" . $s;
+  }
+
+  function pident($arg) {
+    return $arg;
+  }
+
+  function vident($v) {
+    return $v;
+  }
+
+  function vidents($v) {
+    return $v;
+  }
+
+  function vsecond($v1, $v2) {
+    return $v2;
+  }
+}
+
+$a = new MyFoo();
+
+$a->tping("hello");
+$a->tpong("hello");
+
+# TODO: automatic conversion between PHP arrays and std::pair or 
+# std::vector is not yet implemented.
+/*$p = array(1, 2);
+$a->pident($p);
+$v = array(3, 4);
+$a->vident($v);
+
+$a->tpident($p);
+$a->tvident($v);
+
+$v1 = array(3, 4);
+$v2 = array(5, 6);
+
+$a->tvsecond($v1, $v2);
+
+$vs = array("hi", "hello");
+$vs;
+$a->tvidents($vs);*/
+
+check::done();
+?>