When I was working on LU-14158, I have done some changes on llog_reader to understand/debug llog catalog.

So I share my changes here, in case of someone is interested.

Te patches include the following changes:

• Compute/display the first and last index for a catalog
• Check if a catallog record index is in range
• Display records from the first index in catalog
• Check llh_count with the the llog header bitset
• In some cases corruption, display the valid records.
• Add a "print" function for changelog_user records