add example RPC server/client

example/mailbox.cpp

@@ -83,7 +83,7 @@ int main(int argc, char* argv[])
     // Associate a data type (and maybe initial value) with this PV
     pv.open(initial);
 
-    // Build server which will server this PV
+    // Build server which will serve this PV
     // Configure using process environment.
     server::Server serv = server::Config::fromEnv()
             .build()