Identify external links as such
Introduce "DragonFly BSD and GRUB" and indent contained sections
Rename  section and change cross reference mechanism
Rework mb-grub reference
Rework booting-bsd reference
Add html rule and use same ligature/text niceties
Rework dfly-86/64 cross references
Remove unused anchor
Remove references to already nonexistent Appendix A
Fill state of the art section with text
Build HTML too by default
Update PDF preview