[2850] Remove empty ZoneTableSegment destructor

src/lib/datasrc/memory/zone_table_segment_mapped.cc

@@ -31,9 +31,6 @@ ZoneTableSegmentMapped::ZoneTableSegmentMapped(const RRClass& rrclass) :
 {
 }
 
-ZoneTableSegmentMapped::~ZoneTableSegmentMapped() {
-}
-
 void
 ZoneTableSegmentMapped::reset(MemorySegmentOpenMode mode,
                               isc::data::ConstElementPtr params)

src/lib/datasrc/memory/zone_table_segment_mapped.h

@@ -33,6 +33,7 @@ class ZoneTableSegmentMapped : public ZoneTableSegment {
     // This is so that ZoneTableSegmentMapped can be instantiated from
     // ZoneTableSegment::create().
     friend class ZoneTableSegment;
+
 protected:
     /// \brief Protected constructor
     ///
@@ -40,10 +41,8 @@ protected:
     /// (\c ZoneTableSegment::create()), so this constructor is
     /// protected.
     ZoneTableSegmentMapped(const isc::dns::RRClass& rrclass);
-public:
-    /// \brief Destructor
-    virtual ~ZoneTableSegmentMapped();
 
+public:
     /// \brief Return the ZoneTableHeader for the mapped zone table
     /// segment implementation.
     ///