[MEDIUM] http: always evaluate http-request rules before stats http-request

[MEDIUM] http: always evaluate http-request rules before stats http-request

Right now, http-request rules are not evaluated if the URL matches the
stats request. This is quite unexpected. For instance, in the config
below, an abuser present in the abusers list will not be prevented access
to the stats.

   listen pub
        bind :8181
	acl abuser src -f abusers.lst
        http-request deny if abuser
        stats uri /stats

It is not a big deal but it's not documented as such either. For 1.5, let's
have both lists be evaluated in turn, until one blocks. For 1.4 we'll simply
update the doc to indicate that.

Also instead of duplicating the code, the patch factors out the list walking
code. The HTTP auth has been moved slightly earlier, because it was set after
the header addition code, but we don't need to add headers to a request we're
dropping.