Since MaxBackends is actually max_connections + autovacuum_max_workers +
1, when you get an error message from shmget() it will tell you
"reduce ... its max_connections parameter (currently 104)"
when you actually set
max_connections = 100
This looks a bit silly.
Should we just make the error messages report MaxBackends -
autovacuum_max_workers - 1, or is it worthwhile calling out
autovacuum_max_workers separately?
