Followup to r83869 and issue #8524: rename socket.forget() to socket.detach()

and make it return the file descriptor.

Lib/ssl.py

@@ -157,7 +157,7 @@ def __init__(self, sock=None, keyfile=None, certfile=None,
                     raise
             else:
                 connected = True
-            sock.forget()
+            sock.detach()
         elif fileno is not None:
             socket.__init__(self, fileno=fileno)
         else: