[check_postgres] please put version back into download tarball name

[Peter Eisentraut]

With version 2.19.0, the download tarball is named just
check_postgres.tar.gz, instead of check_postgres-2.19.0.tar.gz, like it
used to be.  It's very confusing when you don't know what version you
have.  Could you please fix that?

Also, could you please make old versions available for download as well?
It's actually possible to get them by manipulating the link
http://bucardo.org/downloads/check_postgres-xxx.tar.gz, but it would be
much nicer if, say, http://bucardo.org/downloads/ were browsable.