upnpctrl: add command to show all existing port mappings

This can be useful for debugging purposes.

Change-Id: I9da11d20a7a8cd9f7d1eae9d4aee45281c5cd4ad
diff --git a/include/upnp/mapping.h b/include/upnp/mapping.h
index e92a654..b9c2078 100644
--- a/include/upnp/mapping.h
+++ b/include/upnp/mapping.h
@@ -137,5 +137,17 @@
 #endif
 };
 
+struct MappingInfo
+{
+    std::string remoteHost;
+    std::string protocol;
+    std::string internalClient;
+    std::string enabled;
+    std::string description;
+    uint16_t externalPort;
+    uint16_t internalPort;
+    uint32_t leaseDuration;
+};
+
 } // namespace upnp
 } // namespace dhtnet