hexdump.js

The details (dates, author, revision numbers) are often stale and
misleading, so start removing them. Where the Revision tag was used
for a version/revision, just bump it by one and use a string constant
instead (Git doesn't provide any similar facility for auto-incrementing
revision numbers).

More remains. Perhaps a commit hook to alert me when committing that I should
clean up as I go rather than try to do this in bulk. <shrug>