Sync improvements to syntax highlighting from highlightjs-rpm-specfile
    
    This file was upstreamed in a different form as highlightjs-rpm-specfile,
    and that version was improved to cover many of the new features in
    RPM 4.14 and RPM 4.15.
    
    This change syncs those improvements back into our version.
    
    In addition, the default syntax highlight override now uses the upstream
    name for the rpm specfile syntax highlighter.
    
    Signed-off-by: Neal Gompa <ngompa13@gmail.com>
    
    Merges #4570
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>