Use underscore instead of a dash in compat suffixes
    
    The Fedora Packaging Guidelines are clear on this:
    
    > If the base package name ends with a digit, a single underscore (_)
    > MUST be appended to the name, and the version MUST be appended to
    > that, in order to avoid confusion over where the name ends and the
    > version begins.
    >
    > If the base package name does not end with a digit, the version MUST
    > be directly appended to the package name with no intervening
    > separator.
    
    Fixes #180.