Refine cosmetic improvements for ticket changelog

[Ryan J Ollos]

There are some minor defects and refinements needed after #11835:

• Add trac-author-user { color: #666; }
• Attachment comment overlaps property change table (comment:3:ticket:10323).
• The order of ticket comment form buttons is reversed (comment:27:ticket:11835).
• Pre blocks in ticket comment need a clear: right for the preview (comment:30:ticket:11835)

  #ticketchange pre.wiki, #ticketchange div.code { clear: right }