Fix constant lookup on 1.8
Fix constant lookup on 1.8

On 1.8 HTTP_1_1 and CR_LN can't be found directly like that, we have
to use the proper path.

wadetandy/excon,excon/excon,ilackarms/excon,hammerdr/excon,cloudfoundry-incubator/excon,TheNeatCompany/excon,mahemoff/excon,liftforward/excon