Fix DLGPROC prototype

src/archutils/Win32/WindowsDialogBox.h

@@ -18,7 +18,7 @@ protected:
 	virtual BOOL HandleMessage( UINT msg, WPARAM wParam, LPARAM lParam ) { return false; }
 
 private:
-	static BOOL APIENTRY DlgProc(HWND hDlg, UINT msg, WPARAM wParam, LPARAM lParam);
+	static INT_PTR APIENTRY DlgProc(HWND hDlg, UINT msg, WPARAM wParam, LPARAM lParam);
 	HWND m_hWnd;
 };