sync various packaging changes from f31:
    
    - define with_ghc_prof and with_manual
    - ghc-devel replaces ghc-libraries
    - ghc-doc and ghc-prof for f31+
    - ghc-doc-index replaces ghc-doc-cron
    - use _ghcdynlibdir
    - remove alternatives
    - filetriggers for ghc-pkg recache and gen_contents_index