[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_enum_runme.php

@@ -0,0 +1,25 @@
+<?php
+
+require "tests.php";
+require "director_enum.php";
+
+// No new functions
+check::functions(array(foo_say_hello,foo_say_hi,foo_say_bye,foo_say_hi_ref,foo_ping,foo_ping_ref,foo_ping_member_enum,a_f,a2_f));
+// No new classes
+check::classes(array(director_enum,Foo,A,B,A2,B2));
+// now new vars
+check::globals(array());
+
+class MyFoo extends Foo {
+  function say_hi($val) {
+    return $val;
+  }
+}
+
+$b = new Foo();
+$a = new MyFoo();
+
+check::equal($a->say_hi(director_enum::hello), $b->say_hello(director_enum::hi), "say failed");
+
+check::done();
+?>