Don't request a specific version of a SlackBuild

When searching for SlackBuild dependencies, don't request a specific
version of a package. This will probably use the first one it finds by
the name that is provided, so it should be good anyway.
Request dependencies for a single package

In slaptsrcdeps, request dependencies for a single package, not a list
of packages.
Get dependencies info from slapt-src --show

Use slapt-src --show to get dependencies information instead of
slapt-src --install