[3.12] gh-110383: Document socket.makefile() accepts combined modes (GH-119150) (#119325)

The supported mode values are 'r', 'w', and 'b', or a combination of those.
(cherry picked from commit 62a29be)

Co-authored-by: Daniel Williams <dann0a@gmail.com>

Author: miss-islington

Doc/library/socket.rst

@@ -1584,7 +1584,8 @@ to sockets.
    Return a :term:`file object` associated with the socket.  The exact returned
    type depends on the arguments given to :meth:`makefile`.  These arguments are
    interpreted the same way as by the built-in :func:`open` function, except
-   the only supported *mode* values are ``'r'`` (default), ``'w'`` and ``'b'``.
+   the only supported *mode* values are ``'r'`` (default), ``'w'``, ``'b'``, or
+   a combination of those.
 
    The socket must be in blocking mode; it can have a timeout, but the file
    object's internal buffer may end up in an inconsistent state if a timeout

Lib/socket.py

@@ -306,7 +306,8 @@ def makefile(self, mode="r", buffering=None, *,
         """makefile(...) -> an I/O stream connected to the socket
 
         The arguments are as for io.open() after the filename, except the only
-        supported mode values are 'r' (default), 'w' and 'b'.
+        supported mode values are 'r' (default), 'w', 'b', or a combination of
+        those.
         """
         # XXX refactor to share code?
         if not set(mode) <= {"r", "w", "b"}: