[MEDIUM] default-server support

This patch implements default-server support allowing to change
default server options. It can be used in [defaults] or [backend]/[listen]
sections. Currently the following options are supported:

 - error-limit
 - fall
 - inter
 - fastinter
 - downinter
 - maxconn
 - maxqueue
 - minconn
 - on-error
 - port
 - rise
 - slowstart
 - weight
3 files changed