[pca] failing patch downloads

[Martin Paul]

Don,

> It seems a little coincidental that this version of patchdiag has not 
> been updated after moving to the new SunSolve release.

Yes, that's what makes me extremely nervous ..

As a workaround for now, pca users can set xrefurl to get the current 
xref file:

   pca --xrefurl='https://sunsolve.sun.com/pdownload.do?target=' ...

> I'll get back to you when I know more.

Thanks,

Martin.