Fix broken Creating RPM Packages links
    
    The Packaging Tutorial referred to Quick Docs page Creating RPM
    Packages.
    That page has been removed,
    and actually there is a redirect pointing back to Packaging Tutorial.
    Since Creating RPM Packages only contained generic information about
    RPM and specfile format,
    the links are replaced with links to upstream RPM Reference Manual.
    It is a better place to document RPM material that is not Fedora
    specific.
    
    Resolves #78