[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/sym_runme.php

@@ -0,0 +1,22 @@
+<?php
+
+require "tests.php";
+require "sym.php";
+
+// No new functions
+check::functions(array());
+// No new classes
+check::classes(array(flim,flam));
+// now new vars
+check::globals(array());
+
+$flim=new flim();
+$flam=new flam();
+
+check::equal($flim->hulahoops(),"flim-jam","flim()->hulahoops==flim-jam");
+check::equal($flim->jar(),"flim-jar","flim()->jar==flim-jar");
+check::equal($flam->jam(),"flam-jam","flam()->jam==flam-jam");
+check::equal($flam->jar(),"flam-jar","flam()->jar==flam-jar");
+
+check::done();
+?>