Add Win32Surface

Hi, SImon!

Hmm, we might as well add Win32Surface, no? :-) BTW, I also added cairo.dll to the list of names to try as this is the default one created by cairo.

Thanks!

Carlos
Every time one compiles Cairo (which lately I've been doing a bunch, going after some bugs in the recording surface), I get "cairo.dll" as this is the Cairo default. I don't know why one finds "libcairo-2.dll" in the wild but it doesn't come from Cairo itself. In any case, I'll do a separate commit request.