[2157] remove empty explicit destructor

src/bin/auth/statistics.cc.pre

@@ -121,9 +121,6 @@ Counters::Counters() :
     zone_qr_counters_(QR_COUNTER_TYPES)
 {}
 
-Counters::~Counters()
-{}
-
 void
 Counters::incRequest(const QRAttributes& qrattrs) {
     // protocols carrying request

src/bin/auth/statistics.h

@@ -65,12 +65,6 @@ public:
         reset();
     };
 
-    /// \brief The destructor.
-    ///
-    /// This method never throws an exception.
-    ///
-    ~QRAttributes() {};
-
     /// \brief Set query opcode.
     /// \throw None
     void setQueryOpCode(const int opcode) {
@@ -188,12 +182,6 @@ public:
     ///
     Counters();
 
-    /// \brief The destructor.
-    ///
-    /// This method never throws an exception.
-    ///
-    ~Counters();
-
     /// \brief Increment counters according to the parameters.
     ///
     /// This constructor is mostly exception free. But it may still throw

src/lib/statistics/counter.h

@@ -54,11 +54,6 @@ public:
         }
     };
 
-    /// The destructor.
-    ///
-    /// This method never throws an exception.
-    ~Counter() {};
-
     /// \brief Increment a counter item specified with \a type.
     ///
     /// \param type %Counter item to increment

src/lib/statistics/counter_dict.h

@@ -56,7 +56,6 @@ public:
             isc_throw(isc::InvalidParameter, "Items must not be 0");
         }
     };
-    ~CounterDictionary() {};
     void addElement(const std::string& name) {
         // throw if the element already exists
         if (dictionary_.count(name) != 0) {
@@ -113,10 +112,6 @@ public:
             /// throw a standard exception if memory allocation fails
             /// inside the method.
             ConstIterator() {}
-            /// The destructor.
-            ///
-            /// This method never throws an exception.
-            ~ConstIterator() {}
             /// Constructor from implementation detail DictionaryMap::const_iterator
             ConstIterator(
                 DictionaryMap::const_iterator iterator) :