[mojosetup] Want / Need 7zip compression

[Ryan C. Gordon]

> Since we have some action in the lsit.. is there ANY way to get 7zip 
> compression support in mojo? Makes a big difference.

It just needs someone to implement it.  :)

MojoSetup would need a way to figure out where the 7zip data starts (we 
could just expect it to read a byte offset from the end of the binary 
file or something), and someone would need to write a little bit of glue 
between the MojoArchive interface and the lzma sdk.

I don't have time to do this right now, but I'd like to if I can find some.

--ryan.