Revert "wp++"

This reverts commit 89fcc36fb1.

wp-includes/class-wp-error.php

@@ -202,3 +202,17 @@ class WP_Error {
 		unset( $this->error_data[ $code ] );
 	}
 }
+
+/**
+ * Check whether variable is a WordPress Error.
+ *
+ * Returns true if $thing is an object of the WP_Error class.
+ *
+ * @since 2.1.0
+ *
+ * @param mixed $thing Check if unknown variable is a WP_Error object.
+ * @return bool True, if WP_Error. False, if not WP_Error.
+ */
+function is_wp_error( $thing ) {
+	return ( $thing instanceof WP_Error );
+}