Fix implementation of Iterator interface

It looks like you have to implement the Iterator interface *before*
assigning get_iterator. Otherwise the structure for user iterators isn't
correctly zeroed out.

Additionaly I'm setting class_entry->iterator_funcs.funcs now. Not sure if
this is strictly necessary, but better safe than sorry ;)

Zend/tests/generators/generator_in_multipleiterator.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Generators work properly in MultipleIterator
+--FILE--
+<?php
+
+function gen1() {
+    yield 'a';
+    yield 'aa';
+}
+
+function gen2() {
+    yield 'b';
+    yield 'bb';
+}
+
+$it = new MultipleIterator;
+$it->attachIterator(gen1());
+$it->attachIterator(gen2());
+
+foreach ($it as $values) {
+    var_dump($values);
+}
+
+?>
+--EXPECT--
+array(2) {
+  [0]=>
+  string(1) "a"
+  [1]=>
+  string(1) "b"
+}
+array(2) {
+  [0]=>
+  string(2) "aa"
+  [1]=>
+  string(2) "bb"
+}

Zend/zend_generators.c

@@ -759,9 +759,11 @@ void zend_register_generator_ce(TSRMLS_D) /* {{{ */
 	zend_ce_generator = zend_register_internal_class(&ce TSRMLS_CC);
 	zend_ce_generator->ce_flags |= ZEND_ACC_FINAL_CLASS;
 	zend_ce_generator->create_object = zend_generator_create;
-	zend_ce_generator->get_iterator = zend_generator_get_iterator;
 
+	/* get_iterator has to be assigned *after* implementing the inferface */
 	zend_class_implements(zend_ce_generator TSRMLS_CC, 1, zend_ce_iterator);
+	zend_ce_generator->get_iterator = zend_generator_get_iterator;
+	zend_ce_generator->iterator_funcs.funcs = &zend_generator_iterator_functions;
 
 	memcpy(&zend_generator_handlers, zend_get_std_object_handlers(), sizeof(zend_object_handlers));
 	zend_generator_handlers.get_constructor = zend_generator_get_constructor;