[ruby-core:18223] release naming consistency

> % ls ~/.multiruby/{versions,build}
> /Users/ryan/.multiruby/build:
> ruby-1.8.7-p22		ruby-1.9.0-2		ruby-1.9.0-r18217
>
> /Users/ryan/.multiruby/versions:
> ruby-1.8.7-p22.tar.gz	ruby-1.9.0-2.tar.gz	ruby-1.9.0-3.tar.gz

PLEASE pick a consistent naming scheme for both the tarballs and the  
packaged directory structures and stick to it.

Thus far I've had to teach multiruby how to look up the latest version  
because the location changes over and over, and now I'm going to have  
to teach it how to look in the tarball to figure out the actual  
directory name and rename it if it doesn't match.

I personally think the tarballs should be named:

   ruby-$M-$m-$b-p$p.tar.gz

and the contained directory should be the same:

   ruby-$M-$m-$b-p$p

That remains consistent with most of the releases done thusfar, and  
the ones prior were usually just without the "-p$p" part.