Changeset d9cd8ae in git

src/img.c,src/mainfrm.cc: Although these are often referred to as
"CMAP .XYZ files", it seems that actually, the extension .XYZ isn't
used, rather .SHT (shot variant, produced by CMAP v16 and later),
.UNA (unadjusted) and .ADJ (adjusted) extensions are. Since we've
long checked for .XYZ, we continue to do so in case anyone is
relying on it, but also check for the other extensions.