improve reproducible build support
scripts now support METALOG
set(8): allow to bulk "partial replacement"
rework the scheduler to minimize the number of split upgrades
add(8): backout support for provides/requiress

update sqlite 3.50.4
update curl 3.16.0
fix fetch resuming
shlib(8): now accept full patch
stats(8): only show local db
run pkg delete script even during split upgrades)
back libraries during split upgrades if needed
repositories: allow negative priorities
upgrade: when pkg self restart: do not warn about the env vars.
fetch(8): do not crash on invalid url
many documentation fixes