[glibmm] resolver example: Use std:stoul instead of stdstrtoul

[Murray Cumming <murrayc src gnome org>]

commit 93443cdec25048e5e0d2bb8a2c1888ffb96b9c7d
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Sep 1 12:30:30 2015 +0200

    resolver example: Use std:stoul instead of stdstrtoul

 examples/network/resolver.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/examples/network/resolver.cc b/examples/network/resolver.cc
index c8506f2..a3c431a 100644
--- a/examples/network/resolver.cc
+++ b/examples/network/resolver.cc
@@ -401,7 +401,7 @@ do_connectable (const std::string& arg, gboolean synchronous)
         {
             host = arg.substr (0, pos);
             port_str = arg.substr(pos);
-            port = std::strtoul (port_str.c_str (), nullptr, 10);
+            port = std::stoul (port_str);
         }
         else
             port = 0;