[SDL] Surface conversion

[Lilith Calbridge]

I'm not sure I understand the SDL_ConvertSurface function.  The
documentation says it "Converts a surface to the same format as another
surface." But it also says, "Creates a new surface of the specified
format,".  How can you convert a surface that's new?

Essentially what I need to do is to upconvert a surface containing a 24
bpp image to 32 bpp in order, I think, to blit it properly to my
layout.

Advice please.

Thanks,
Lilith