Use override in more classes in core/

core/src/fxcrt/fxcrt_posix.h

Index: core/src/fxcrt/fxcrt_posix.h
diff --git a/core/src/fxcrt/fxcrt_posix.h b/core/src/fxcrt/fxcrt_posix.h
index 19e11da4a8716d3a2b95c08f7fff51a6a2e6850b..b24721dddd1880f7360db5256e882583b35f4955 100644
--- a/core/src/fxcrt/fxcrt_posix.h
+++ b/core/src/fxcrt/fxcrt_posix.h
@@ -15,22 +15,24 @@
 class CFXCRT_FileAccess_Posix : public IFXCRT_FileAccess {
  public:
   CFXCRT_FileAccess_Posix();
-  virtual ~CFXCRT_FileAccess_Posix();
-  virtual FX_BOOL Open(const CFX_ByteStringC& fileName, FX_DWORD dwMode);
-  virtual FX_BOOL Open(const CFX_WideStringC& fileName, FX_DWORD dwMode);
-  virtual void Close();
-  virtual void Release();
-  virtual FX_FILESIZE GetSize() const;
-  virtual FX_FILESIZE GetPosition() const;
-  virtual FX_FILESIZE SetPosition(FX_FILESIZE pos);
-  virtual size_t Read(void* pBuffer, size_t szBuffer);
-  virtual size_t Write(const void* pBuffer, size_t szBuffer);
-  virtual size_t ReadPos(void* pBuffer, size_t szBuffer, FX_FILESIZE pos);
-  virtual size_t WritePos(const void* pBuffer,
-                          size_t szBuffer,
-                          FX_FILESIZE pos);
-  virtual FX_BOOL Flush();
-  virtual FX_BOOL Truncate(FX_FILESIZE szFile);
+  ~CFXCRT_FileAccess_Posix() override;
+
+  // IFXCRT_FileAccess
+  FX_BOOL Open(const CFX_ByteStringC& fileName, FX_DWORD dwMode) override;
+  FX_BOOL Open(const CFX_WideStringC& fileName, FX_DWORD dwMode) override;
+  void Close() override;
+  void Release() override;
+  FX_FILESIZE GetSize() const override;
+  FX_FILESIZE GetPosition() const override;
+  FX_FILESIZE SetPosition(FX_FILESIZE pos) override;
+  size_t Read(void* pBuffer, size_t szBuffer) override;
+  size_t Write(const void* pBuffer, size_t szBuffer) override;
+  size_t ReadPos(void* pBuffer, size_t szBuffer, FX_FILESIZE pos) override;
+  size_t WritePos(const void* pBuffer,
+                  size_t szBuffer,
+                  FX_FILESIZE pos) override;
+  FX_BOOL Flush() override;
+  FX_BOOL Truncate(FX_FILESIZE szFile) override;
 
  protected:
   int32_t m_nFD;