worker, event, prefork: Correct several issues when built as

worker, event, prefork: Correct several issues when built as
DSOs; most notably, the scoreboard was reinitialized during graceful
restart, such that processes of the previous generation were not
observable.

Other noticeable ones:
* the generation number did not increment properly
* worker's check-config hook didn't detect startup properly,
  so messages about inconsistent directives could have been sent
  to the wrong place

max_daemons_limit wasn't tracked across restart, but as the scoreboard
was always cleared this was a non-issue.

Reinitialization of idle_spawn_rate, hold_off_on_exponential_spawning,
and maxclients-message-reported may or may not have been features,
but the big picture is that the behaviour shouldn't have differed.

These changes should have been part of r758185.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1078286 13f79535-47bb-0310-9956-ffa450edef68