shill: Add C++11 override specifier to destructors of derived classes.

BUG=None
TEST=`USE=wimax FEATURES=test emerge-$BOARD platform2`

Change-Id: I88d4e29165869b26924cccb94ac940dc8961c312
Reviewed-on: https://chromium-review.googlesource.com/212267
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
diff --git a/mm1_modem_location_proxy.h b/mm1_modem_location_proxy.h
index 4da5f69..391ca35 100644
--- a/mm1_modem_location_proxy.h
+++ b/mm1_modem_location_proxy.h
@@ -23,7 +23,7 @@
                      const std::string &path,
                      const std::string &service);
 
-  virtual ~ModemLocationProxy();
+  ~ModemLocationProxy() override;
 
   // Inherited methods from ModemLocationProxyInterface.
   virtual void Setup(uint32_t sources,
@@ -43,7 +43,7 @@
     Proxy(DBus::Connection *connection,
           const std::string &path,
           const std::string &service);
-    virtual ~Proxy();
+    ~Proxy() override;
 
    private:
     // Method callbacks inherited from