Mark Client, Window, Buffer and OptionManager as final

Avoids warning about non virtual destructor calls on them,
as they have a vtable due to OptionManagerWatcher.

src/buffer.hh

@@ -103,7 +103,7 @@ using BufferLines = Vector<StringDataPtr, MemoryDomain::BufferContent>;
 // The Buffer class permits to read and mutate this file
 // representation. It also manage modifications undo/redo and
 // provides tools to deal with the line/column nature of text.
-class Buffer : public SafeCountable, public OptionManagerWatcher, public Scope
+class Buffer final : public SafeCountable, public Scope, private OptionManagerWatcher
 {
 public:
     enum class Flags

src/client.hh

@@ -22,7 +22,7 @@ enum class EventMode;
 enum class InfoStyle;
 enum class MenuStyle;
 
-class Client : public SafeCountable, public OptionManagerWatcher
+class Client final : public SafeCountable, public OptionManagerWatcher
 {
 public:
     using OnExitCallback = std::function<void (int status)>;

src/option_manager.hh

@@ -78,7 +78,7 @@ public:
     virtual void on_option_changed(const Option& option) = 0;
 };
 
-class OptionManager : private OptionManagerWatcher
+class OptionManager final : private OptionManagerWatcher
 {
 public:
     OptionManager(OptionManager& parent);

src/window.hh

@@ -13,7 +13,7 @@ namespace Kakoune
 {
 
 // A Window is a view onto a Buffer
-class Window : public SafeCountable, public OptionManagerWatcher, public Scope
+class Window final : public SafeCountable, public Scope, private OptionManagerWatcher
 {
 public:
     Window(Buffer& buffer);