make bytes(o) respect __bytes__ #2415

This adds two new C-API functions: PyObject_Bytes and PyBytes_FromObject.

Reviewer: Barry
diff --git a/Misc/NEWS b/Misc/NEWS
index 8594c99..d779132 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -27,6 +27,13 @@
 
 - Issue #3650: Fixed a reference leak in bytes.split('x').
 
+- bytes(o) now tries to use o.__bytes__() before using fallbacks.
+
+C API
+-----
+
+- PyObject_Bytes and PyBytes_FromObject were added.
+
 Library
 -------