fix close button in system menu for AboutDialog on Windows


If SetEscapeId receives wx.ID_CLOSE as parameter, then on Windows with
wxPython 2.8 system close button in title bar stops working.
If wx.ID_CANCEL or wx.ID_OK is used in SetEscapeId call, then close
button works correctly.

int CheckRetainBuffer(void)
{
	return 1;
}

void ValidateRetainBuffer(void)
{
}

void InValidateRetainBuffer(void)
{
}

void Retain(unsigned int offset, unsigned int count, void *p)
{
}

void Remind(unsigned int offset, unsigned int count, void *p)
{
}