convert FindInPouDialog from wx.Frame to wx.Dialog

In this case FindInPouDialog Windows isn't listed in windows manager
on Alt-Tab. And it's not shown on top of other applications. For
example, previously the dialog was shown even on top of web browser or
word processor.

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)
{
}