Add a return value to onresponse hook to override status/headers
Add a return value to onresponse hook to override status/headers

This would allow us to override them without messing up the body,
and would make it usable with the static file handler for example.

Experimental at this point.

turtleDeng/cowboy,noname007/cowboy,callsign-core/cowboy_hybi00,callsign-core/cowboy_hybi00,odo/cowboy,bsmr-erlang/cowboy,K2InformaticsGmbH/cowboy,yangchengjian/cowboy,Reimerei/cowboy,acrispin/cowboy,rabbitmq/cowboy,sile/cowboy,grahamrhay/cowboy,binarin/cowboy,CrankWheel/cowboy,cad627/cowboy,276361270/cowboy,ninenines/cowboy,yangchengjian/cowboy,dangjun625/cowboy,pap/cowboy,kivra/cowboy,imdeps/cowboy,cad627/cowboy,hairyhum/cowboy,bobos/ecweb,omusico/cowboy,nviennot/cowboy,binarin/cowboy,paulperegud/cowboy