[Bug #1477102] Add necessary import to example

This may be a useful style question for the docs -- should examples show
the necessary imports, or should it be assumed that the reader will
figure it out?  In the What's New, I'm not consistent but usually opt
for omitting the imports.

Doc/lib/libxmlrpclib.tex

@@ -340,6 +340,7 @@ objects, they are converted to \class{DateTime} objects internally, so only
 
 \begin{verbatim}
 # simple test program (from the XML-RPC specification)
+from xmlrpclib import ServerProxy
 
 # server = ServerProxy("http://localhost:8000") # local server
 server = ServerProxy("http://betty.userland.com")