readdir() was returning NULL instead of FALSE when used on an invalid

directory handle.  If someone forgot to check (as someone here did) that
the opendir() succeeded, and then followed the documented usage by checking
readdir()!==FALSE things would go awry.  The ZEND_FETCH_RESOURCE macro
explicitly does a RETURN_NULL on failure which is not what we want in this
case, so work around it.  No need to change it for the OO case since the
object is not created if the opendir fails.

ext/standard/dir.c

@@ -85,7 +85,9 @@ static zend_class_entry *dir_class_entry_ptr;
 	} else if ((ZEND_NUM_ARGS() != 1) || zend_get_parameters_ex(1, &id) == FAILURE) { \
 		WRONG_PARAM_COUNT; \
 	} else { \
-		ZEND_FETCH_RESOURCE(dirp, php_stream *, id,-1, "Directory", php_file_le_stream()); \
+		dirp = (php_stream *) zend_fetch_resource(id TSRMLS_CC, -1, "Directory", NULL, 1, php_file_le_stream()); \
+		if(!dirp) \
+			RETURN_FALSE; \
 	} 
 
 static zend_function_entry php_dir_class_functions[] = {