When 'minconn' is set, the number of simultaneous sessions sent to the server
will be limited by a dynamic value depending on the global load on the
instance itself. The principle is to fix the maximal concurrency on the server
proportionnally to the instance's usage relative to its maxconn, with a minimum
fixed to <minconn>. The formula for the number of simultaneous sessions sent
to the server is then max(srv_minconn, srv_maxconn*px_conn/px_maxconn). This
helps unloading the servers when the load is very low.
It has been rewritten and now supports an initialization state. It now also
prevents from dumping stopped(disabled) listeners and it is possible to
specify a scope with a list of proxies that are allowed to be dumped from
the one being configured ('.' meaning "this one"). The 'stats' entry can
be configured from the 'defaults' instance and it is correctly flushed
from proxies which redefine it.
