[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/php_iterator_runme.php

@@ -0,0 +1,24 @@
+<?php
+
+require "tests.php";
+require "php_iterator.php";
+
+check::functions(array(myiterator_rewind,myiterator_key,myiterator_current,myiterator_next,myiterator_valid));
+check::classes(array(MyIterator));
+// No new global variables.
+check::globals(array());
+
+$s = '';
+foreach (new MyIterator(1, 6) as $i) {
+  $s .= $i;
+}
+check::equal($s, '12345', 'Simple iteration failed');
+
+$s = '';
+foreach (new MyIterator(2, 5) as $k => $v) {
+  $s .= "($k=>$v)";
+}
+check::equal($s, '(0=>2)(1=>3)(2=>4)', 'Simple iteration failed');
+
+check::done();
+?>