Use override in more classes in core/

core/include/fxge/fx_font.h

Index: core/include/fxge/fx_font.h
diff --git a/core/include/fxge/fx_font.h b/core/include/fxge/fx_font.h
index 50cbba8e265b3d54f6d42397aa426a453f260869..ce06a8ac5f4a44ba3aa01d3e28acb10251ab3731 100644
--- a/core/include/fxge/fx_font.h
+++ b/core/include/fxge/fx_font.h
@@ -244,7 +244,7 @@ class IFX_AdditionalFontEnum {
 };
 class CFX_FontMapper {
  public:
-  CFX_FontMapper(CFX_FontMgr* mgr);
+  explicit CFX_FontMapper(CFX_FontMgr* mgr);
   ~CFX_FontMapper();
 
   void SetSystemFontInfo(IFX_SystemFontInfo* pFontInfo);
@@ -283,6 +283,7 @@ class CFX_FontMapper {
   IFX_FontEnumerator* m_pFontEnumerator;
   CFX_FontMgr* const m_pFontMgr;
 };
+
 class IFX_SystemFontInfo {
  public:
   static IFX_SystemFontInfo* CreateDefault(const char** pUserPaths);
@@ -307,12 +308,13 @@ class IFX_SystemFontInfo {
   virtual void* RetainFont(void* hFont) { return NULL; }
 
  protected:
-  ~IFX_SystemFontInfo() {}
+  virtual ~IFX_SystemFontInfo() {}
 };
+
 class CFX_FolderFontInfo : public IFX_SystemFontInfo {
  public:
   CFX_FolderFontInfo();
-  virtual ~CFX_FolderFontInfo();
+  ~CFX_FolderFontInfo() override;
   void AddPath(const CFX_ByteStringC& path);
 
   // IFX_SytemFontInfo: