Fix some return types in ext/spl

Closes GH-7237

Author: kocsismate

ext/spl/spl_observer.stub.php

@@ -34,10 +34,10 @@ public function contains(object $object) {}
     /** @return int */
     public function addAll(SplObjectStorage $storage) {}
 
-    /** @return void */
+    /** @return int */
     public function removeAll(SplObjectStorage $storage) {}
 
-    /** @return void */
+    /** @return int */
     public function removeAllExcept(SplObjectStorage $storage) {}
 
     /** @return mixed */
@@ -58,7 +58,7 @@ public function valid() {}
     /** @return int */
     public function key() {}
 
-    /** @return object */
+    /** @return object|null */
     public function current() {}
 
     /** @return void */
@@ -138,10 +138,10 @@ public function rewind() {}
     /** @return bool */
     public function valid() {}
 
-    /** @return array */
+    /** @return array|false */
     public function key() {}
 
-    /** @return array */
+    /** @return array|false */
     public function current() {}
 
     /** @return void */

ext/spl/spl_observer_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: aaefa4d4ac3b795212191d9fe06982d29948f552 */
+ * Stub hash: 36fd33124b8d53051b283fafa5c4a92f3ca04f14 */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_SplObserver_update, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, subject, SplSubject, 0)