Addition of a redis-doc subpackage for Redis v4 onward
    
    This adds a redis-doc subpackage, containing the upstream
    docs (https://github.com/antirez/redis-doc/), as well as
    the existing man page content we've added.  Care is taken
    to handle the movement of man page files between packages
    and the naming convention of the redis-doc source is also
    careful to follow the prefered Fedora conventions.
    
    Optional conversion of markdown to html is done by pandoc
    if available.
    
    In the future, it would be to modify the redis build to
    generate the redis src/help.h file using the content from
    redis-doc now that we have it.  It's often out of date, I
    am noticing - seems to be updated in an ad-hoc fashion in
    upstream releases.