add missing HISTORY entries based on my changes leading up to 6.0

Please merge to 6.0 (some of the history files already have
post-6.0 notes in them, but hopefully this patch still applies
cleanly)
fill in some missing history notes

Merge to v6.0
Update HISTORY

Please merge to v6.0
Add a HISTORY file for unstable

Note: I tried to reconstruct some history back
to 5.3.4, but it's not complete.

Please merge to v6.0
Correct pkgs urls, please include in v6
update HISTORY based on some of Jay's changes

please include in 6.0
Fix typo on pkg site
Remove secret information from pkg error messages
Fix PR14216
Use Racket navbar on pkgs. and have navbar link to pkgs.

Open question: Where does link to Planet go? Sam's new design has a natural place, but on the old site... it's not clear, community?
Adding suggestion about 1.0 package versions
Add history file for the profiler.
fix sqlite rollback-transaction in case of auto-rollback error

Merge to release branch.

An invalid (needs-rollback?) transaction may correspond to a closed
underlying transaction. In that case, don't issue ROLLBACK command.