message: Make it possible to copy construct/assign RefCountBase
  Otherwise it is not possible to have default implementations in
  classes derived from (Atomic)RefCountBase.
diff: @@ -309,11 +309,11 @@ public:
  REALM_ASSERT(m_ref_count == 0);
  }
  - RefCountBase(const RefCountBase&) = delete;
  - RefCountBase(RefCountBase&&) = delete;
  -
  - void operator=(const RefCountBase&) = delete;
  - void operator=(RefCountBase&&) = delete;
  + RefCountBase(const RefCountBase&)
  + : m_ref_count(0)
  + {
  + }
  + void operator=(const RefCountBase&) {}
  protected:
  void bind_ptr() const noexcept
  @@ -350,11 +350,11 @@ public:
  REALM_ASSERT(m_ref_count == 0);
  }
  - AtomicRefCountBase(const AtomicRefCountBase&) = delete;
  - AtomicRefCountBase(AtomicRefCountBase&&) = delete;
  -
  - void operator=(const AtomicRefCountBase&) = delete;
  - void operator=(AtomicRefCountBase&&) = delete;
  + AtomicRefCountBase(const AtomicRefCountBase&)
  + : m_ref_count(0)
  + {
  + }
  + void operator=(const AtomicRefCountBase&) {}
  protected:
  // FIXME: Operators ++ and -- as used below use
  