Windows: Protect against using a container file as its own keyfile. Normalizing path names to never use '/' but always '\'.

src/Common/Dlgcode.h

@@ -328,6 +328,7 @@ static BOOL CALLBACK CloseVolumeExplorerWindowsEnum( HWND hwnd, LPARAM driveNo);
 BOOL CloseVolumeExplorerWindows (HWND hwnd, int driveNo);
 BOOL CheckCapsLock (HWND hwnd, BOOL quiet);
 BOOL CheckFileExtension (char *fileName);
+void CorrectFileName (char* fileName);
 void IncreaseWrongPwdRetryCount (int count);
 void ResetWrongPwdRetryCount (void);
 BOOL WrongPwdRetryCountOverLimit (void);