slackrepo.info: Updated md5sum.
slackrepo_*.conf: Fixed filename in comment.
slackrepo: Fixed RSS_UUID and error handling.
slackrepo: Fixed git handling.

Was failing when SBREPO was *under* a higher git dir. Use
git rev-parse --is-inside-work-tree instead of looking for
.git subdirectory.
Fix version hint handling of md5sums.

If VERSION is specified, don't override any specified MD5SUM.
Fix version hint handling of md5sums (part 2).

Slackware SlackBuilds were setting VERSION to '*' if no source present.