Fix regression in plugin API
Fix regression in plugin API

Removing a call to a deprecated method had the effect of rendering
plugins that override that method inoperable.

This manifest as a failure to build scala-js in the community
build: https://github.com/scala/community-builds/issues/95

Partially reverts d4546fd.

martijnhoekstra/scala,felixmulder/scala,martijnhoekstra/scala,jvican/scala,felixmulder/scala,jvican/scala,felixmulder/scala,lrytz/scala,lrytz/scala,slothspot/scala,shimib/scala,slothspot/scala,jvican/scala,martijnhoekstra/scala,slothspot/scala,scala/scala,martijnhoekstra/scala,slothspot/scala,scala/scala,scala/scala,felixmulder/scala,shimib/scala,lrytz/scala,lrytz/scala,felixmulder/scala,jvican/scala,shimib/scala,jvican/scala,lrytz/scala,shimib/scala,slothspot/scala,scala/scala,slothspot/scala,jvican/scala,martijnhoekstra/scala,slothspot/scala,felixmulder/scala,scala/scala,shimib/scala,martijnhoekstra/scala,lrytz/scala,jvican/scala,scala/scala,shimib/scala,felixmulder/scala