Discard whitespace at the end of header values early
Discard whitespace at the end of header values early

This is more in line with what RC7230 says, and will allow simplifying
the parsing code of a few headers in cowlib.

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