[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/wrapmacro_runme.php

@@ -0,0 +1,12 @@
+<?php
+
+require "tests.php";
+require "wrapmacro.php";
+
+check::functions(array('guint16_swap_le_be_constant', 'maximum'));
+
+check::equal(maximum(2.3, 2.4), 2.4, "maximum() doesn't work");
+check::equal(guint16_swap_le_be_constant(0x1234), 0x3412, "GUINT16_SWAP_LE_BE_CONSTANT() doesn't work");
+
+check::done();
+?>