More work on the new GBDE section:

• Remove a comment encouraging someone to convert an xref to a ulink.
• Simplify run-on sentence in introduction.
• Use more descriptive DocBook tags.
• Refer to our two versions of UFS as UFS1 and UFS2 rather than UFS and UFS2. (1)
• Move an ephemeral URL from the main text to a footnote.
• Note that newfs -O2 is the default for FreeBSD 5.1 and later (1).
• Wordsmith (1, partially)

PR: docs/51598
(1) Submitted by: bmah