Bug#735516: python-liblas: hardcoded dependency on liblas1 which is no longer built by liblas

[peter green]

>
> The package is also uploaded to mentors, but I won't request sponsorship
> until the python-liblas source package is removed from unstable. (#738141)
>   
I've just spoken to a memeber of the ftp team on irc and you have this 
backwards, the normal thing to do is to upload the package doing the 
takeover first, then cleanup the old source package.