sparc64 flag day

the sparc64 just underwent a flag day.  The memory model has been changed.

There will be no upgrade from 3.0 to 3.1 on the sparc64.  You must
reinstall, due to the binaries having been changed in fiddly internal
ways.  Just reinstall.  You could very carefully upgrade, but then
other issues might happen, like packages you are using, etc.

So just reinstall if you have a sparc64, ok?  You will be happy.  Some
compiler bugs are fixed as a result!