Promote stan-raspbian to stable

[StanFromIreland]

The buildbot logs are [will be in theory] green, all issues have been resolved.

[StanFromIreland]

There was an interesting performance change with SlowNonDebugUnix, building now takes ~2x the original time, where as tests take ~.33x of the original time. Better overall, but still quite odd.

[zware]

Ah, I missed that you changed the builder type as well as stability :(. The difference is that UnixBuild is a debug build, and SlowNonDebugUnix is, as the name may suggest, non-debug.

[StanFromIreland]

Oh sorry, I noticed that's what gps-Raspbian used so I thought it would be useful for mine too, as they were taking almost one hour. It's cut the time in half, though it is no longer a debug build, which is surprisingly faster to compile.