beam_dead: Remove code that cannot be covered in forward/4
beam_dead: Remove code that cannot be covered in forward/4

Since the optimizations in forward/4 already depends on some
assumptions on how code is generated anyway, document the
assumptions in a comment and remove the uncoverable code.

bernardd/otp,rlipscombe/otp,Teino1978-Corp/erlang-otp,legoscia/otp,RaimoNiskanen/otp,dgud/otp,electricimp/otp,psyeugenic/otp,platinumthinker/otp,yangchengjian/otp,RoadRunnr/otp,bugs-erlang-org/otp,lianghaivv/otp,ahmedshafeeq/otp,sitexa/otp,rlipscombe/otp,lightcyphers/otp,RGafiyatullin/otp,kvakvs/otp,theom/otp,bugs-erlang-org/otp,g-andrade/otp,palas/otp,vinoski/otp,theom/otp,erlang/otp,schlagert/otp,mujiatong/otp,fenollp/otp,RJ/otp,weisslj/otp,marquisthunder/otp,potatosalad/otp,cobusc/otp,electricimp/otp,basho/otp,goertzenator/otp,basho/otp,NOMORECOFFEE/otp,sdebnath/otp,bjorng/otp,potatosalad/otp,uabboli/otp,lemenkov/otp,GinjaNinja32/otp,release-project/otp,cnbin/otp,sammoth-wazoku/otp,goertzenator/otp,jinshana/otp,jemsbhai/otp,isvilen/otp,weisslj/otp,getong/otp,cnbin/otp,lantti/otp,Teino1978-Corp/erlang-otp,enikki/otp,ader1990/otp,jinshana/otp,awetzel/otp,klarna/otp,jamesruan/otp,haguenau/otp,psyeugenic/otp,haguenau/otp,emacsmirror/erlang,derek121/otp,mujiatong/otp,emile/otp,potatosalad/otp,vladdu/otp,paladim/otp,jj1bdx/otp,weisslj/otp,weisslj/otp,sammoth-wazoku/otp,RichMorin/otp,VincentHHL/otp,paulcager/otp,tuncer/otp,vic/otp,marquisthunder/otp,entropiae/otp,jj1bdx/otp,lucafavatella/otp,bugs-erlang-org/otp,RGafiyatullin/otp,mujiatong/otp,riverrun/otp,marquisthunder/otp,fenollp/otp,neeraj9/otp,Teino1978-Corp/erlang-otp,matwey/otp,vinoski/otp,jinshana/otp,klarna/otp,jamesruan/otp,palas/otp,bjorng/otp,VincentHHL/otp,klarna/otp,bsmr-erlang/otp,basho/otp,potatosalad/otp,lucafavatella/otp,c-rack/otp,NOMORECOFFEE/otp,c-rack/otp,riverrun/otp,lucafavatella/otp,dgud/otp,krishnakumar4a4/otp,ader1990/otp,bjorng/otp,uabboli/otp,tuncer/otp,RJ/otp,matwey/otp,cnbin/otp,derek121/otp,stolen/otp,lightcyphers/otp,isvilen/otp,lrascao/otp,getong/otp,klarna/otp,platinumthinker/otp,release-project/otp,lemenkov/otp,lightcyphers/otp,RGafiyatullin/otp,kvakvs/otp,saleyn/otp,electricimp/otp,uabboli/otp,mujiatong/otp,enikki/otp,uabboli/otp,platinumthinker/otp,lightcyphers/otp,getong/otp,matwey/otp,vladdu/otp,ferd/otp,VincentHHL/otp,awetzel/otp,mujiatong/otp,bsmr-erlang/otp,NOMORECOFFEE/otp,saleyn/otp,krishnakumar4a4/otp,ahmedshafeeq/otp,bjorng/otp,dgud/otp,cobusc/otp,riverrun/otp,mikpe/otp,bjorng/otp,tuncer/otp,benoitc/otp-1,vinoski/otp,derek121/otp,kvakvs/otp,platinumthinker/otp,c-rack/otp,vinoski/otp,Teino1978-Corp/erlang-otp,GinjaNinja32/otp,isvilen/otp,dumbbell/otp,jj1bdx/otp,aboroska/otp,lightcyphers/otp,legoscia/otp,bjorng/otp,stolen/otp,bernardd/otp,vladdu/otp,bsmr-erlang/otp,jemsbhai/otp,beni55/otp,potatosalad/otp,release-project/otp,erlang/otp,weisslj/otp,jemsbhai/otp,bsmr-erlang/otp,sdebnath/otp,jemsbhai/otp,rlipscombe/otp,emile/otp,potatosalad/otp,neeraj9/otp,ader1990/otp,sdebnath/otp,matwey/otp,cobusc/otp,erlang/otp,release-project/otp,riverrun/otp,aboroska/otp,dumbbell/otp,jamesruan/otp,lantti/otp,dgud/otp,legoscia/otp,erlang/otp,uabboli/otp,sitexa/otp,goertzenator/otp,palas/otp,gjaldon/otp,Teino1978-Corp/otp,bsmr-erlang/otp,lhslll/otp,Teino1978-Corp/otp,RaimoNiskanen/otp,g-andrade/otp,schlagert/otp,c-rack/otp,g-andrade/otp,sitexa/otp,dumbbell/otp,lucafavatella/otp,cnbin/otp,yangchengjian/otp,sitexa/otp,schlagert/otp,msantos/otp,dgud/otp,NOMORECOFFEE/otp,klarna/otp,RJ/otp,benoitc/otp-1,Teino1978-Corp/otp,aboroska/otp,massemanet/otp,lrascao/otp,johanclaesson/otp,neeraj9/otp,gjaldon/otp,jj1bdx/otp,sdebnath/otp,emacsmirror/erlang,electricimp/otp,lucafavatella/otp,gjaldon/otp,lemenkov/otp,jj1bdx/otp,lhslll/otp,basho/otp,paladim/otp,RichMorin/otp,psyeugenic/otp,RoadRunnr/otp,RJ/otp,aboroska/otp,jemsbhai/otp,RoadRunnr/otp,jinshana/otp,krishnakumar4a4/otp,bernardd/otp,sitexa/otp,electricimp/otp,RaimoNiskanen/otp,ferd/otp,awetzel/otp,gjaldon/otp,jamesruan/otp,hairyhum/otp,paladim/otp,jamesruan/otp,kvakvs/otp,tuncer/otp,psyeugenic/otp,rlipscombe/otp,g-andrade/otp,ahmedshafeeq/otp,bjorng/otp,uabboli/otp,RaimoNiskanen/otp,Teino1978-Corp/erlang-otp,johanclaesson/otp,dumbbell/otp,fenollp/otp,dumbbell/otp,legoscia/otp,lightcyphers/otp,neeraj9/otp,weisslj/otp,enikki/otp,GinjaNinja32/otp,emacsmirror/erlang,fenollp/otp,massemanet/otp,GinjaNinja32/otp,krishnakumar4a4/otp,derek121/otp,emacsmirror/erlang,bugs-erlang-org/otp,marquisthunder/otp,vic/otp,msantos/otp,sammoth-wazoku/otp,vladdu/otp,vic/otp,RichMorin/otp,awetzel/otp,derek121/otp,Teino1978-Corp/erlang-otp,legoscia/otp,c-rack/otp,paladim/otp,palas/otp,mikpe/otp,entropiae/otp,yangchengjian/otp,potatosalad/otp,goertzenator/otp,mujiatong/otp,bjorng/otp,benoitc/otp-1,massemanet/otp,massemanet/otp,lrascao/otp,lantti/otp,palas/otp,emile/otp,dumbbell/otp,lemenkov/otp,stolen/otp,theom/otp,mikpe/otp,haguenau/otp,msantos/otp,saleyn/otp,erlang/otp,lianghaivv/otp,paulcager/otp,jinshana/otp,krishnakumar4a4/otp,theom/otp,yangchengjian/otp,enikki/otp,paulcager/otp,bjorng/otp,lightcyphers/otp,lemenkov/otp,sammoth-wazoku/otp,tuncer/otp,vladdu/otp,dumbbell/otp,cobusc/otp,emacsmirror/erlang,vic/otp,goertzenator/otp,kvakvs/otp,release-project/otp,benoitc/otp-1,marquisthunder/otp,lemenkov/otp,Teino1978-Corp/otp,matwey/otp,bugs-erlang-org/otp,ader1990/otp,lhslll/otp,mujiatong/otp,RichMorin/otp,RoadRunnr/otp,lhslll/otp,vinoski/otp,erlang/otp,weisslj/otp,entropiae/otp,ferd/otp,VincentHHL/otp,matwey/otp,potatosalad/otp,dgud/otp,entropiae/otp,beni55/otp,g-andrade/otp,aboroska/otp,cobusc/otp,falkevik/otp,jinshana/otp,sdebnath/otp,palas/otp,sitexa/otp,enikki/otp,paulcager/otp,hairyhum/otp,beni55/otp,lrascao/otp,matwey/otp,tuncer/otp,erlang/otp,fenollp/otp,RaimoNiskanen/otp,yangchengjian/otp,msantos/otp,erlang/otp,matwey/otp,dgud/otp,beni55/otp,erlang/otp,paladim/otp,ferd/otp,fenollp/otp,getong/otp,legoscia/otp,sitexa/otp,ader1990/otp,cnbin/otp,erlang/otp,matwey/otp,lrascao/otp,isvilen/otp,lemenkov/otp,theom/otp,dumbbell/otp,sdebnath/otp,schlagert/otp,basho/otp,lrascao/otp,ferd/otp,VincentHHL/otp,potatosalad/otp,RJ/otp,entropiae/otp,ahmedshafeeq/otp,goertzenator/otp,RichMorin/otp,RichMorin/otp,RoadRunnr/otp,paladim/otp,haguenau/otp,falkevik/otp,fenollp/otp,johanclaesson/otp,release-project/otp,release-project/otp,entropiae/otp,emile/otp,psyeugenic/otp,RGafiyatullin/otp,awetzel/otp,psyeugenic/otp,getong/otp,ferd/otp,sammoth-wazoku/otp,isvilen/otp,falkevik/otp,awetzel/otp,ader1990/otp,schlagert/otp,aboroska/otp,vic/otp,rlipscombe/otp,falkevik/otp,uabboli/otp,basho/otp,palas/otp,RichMorin/otp,haguenau/otp,krishnakumar4a4/otp,johanclaesson/otp,bsmr-erlang/otp,Teino1978-Corp/otp,isvilen/otp,VincentHHL/otp,mikpe/otp,johanclaesson/otp,bjorng/otp,RJ/otp,msantos/otp,rlipscombe/otp,theom/otp,awetzel/otp,vinoski/otp,awetzel/otp,paulcager/otp,dgud/otp,uabboli/otp,g-andrade/otp,hairyhum/otp,platinumthinker/otp,tuncer/otp,ahmedshafeeq/otp,paulcager/otp,lantti/otp,massemanet/otp,stolen/otp,getong/otp,goertzenator/otp,stolen/otp,uabboli/otp,gjaldon/otp,psyeugenic/otp,dgud/otp,jemsbhai/otp,bernardd/otp,release-project/otp,vladdu/otp,VincentHHL/otp,RoadRunnr/otp,rlipscombe/otp,paladim/otp,vinoski/otp,benoitc/otp-1,NOMORECOFFEE/otp,marquisthunder/otp,potatosalad/otp,kvakvs/otp,c-rack/otp,saleyn/otp,lrascao/otp,theom/otp,RoadRunnr/otp,lhslll/otp,ader1990/otp,fenollp/otp,aboroska/otp,NOMORECOFFEE/otp,emile/otp,ferd/otp,massemanet/otp,lrascao/otp,riverrun/otp,weisslj/otp,RoadRunnr/otp,lantti/otp,mikpe/otp,dumbbell/otp,basho/otp,saleyn/otp,RaimoNiskanen/otp,tuncer/otp,gjaldon/otp,entropiae/otp,ahmedshafeeq/otp,derek121/otp,legoscia/otp,saleyn/otp,lrascao/otp,johanclaesson/otp,entropiae/otp,hairyhum/otp,bsmr-erlang/otp,massemanet/otp,lhslll/otp,falkevik/otp,sammoth-wazoku/otp,emile/otp,stolen/otp,jamesruan/otp,lianghaivv/otp,jinshana/otp,RJ/otp,klarna/otp,rlipscombe/otp,Teino1978-Corp/otp,falkevik/otp,gjaldon/otp,legoscia/otp,msantos/otp,falkevik/otp,c-rack/otp,platinumthinker/otp,vinoski/otp,lucafavatella/otp,saleyn/otp,Teino1978-Corp/otp,klarna/otp,ahmedshafeeq/otp,kvakvs/otp,lantti/otp,mikpe/otp,cobusc/otp,getong/otp,vic/otp,GinjaNinja32/otp,kvakvs/otp,paulcager/otp,RaimoNiskanen/otp,sitexa/otp,lianghaivv/otp,cobusc/otp,beni55/otp,paladim/otp,haguenau/otp,electricimp/otp,fenollp/otp,NOMORECOFFEE/otp,sdebnath/otp,derek121/otp,schlagert/otp,mikpe/otp,isvilen/otp,vic/otp,emile/otp,mikpe/otp,enikki/otp,emacsmirror/erlang,hairyhum/otp,bugs-erlang-org/otp,lianghaivv/otp,bsmr-erlang/otp,jj1bdx/otp,aboroska/otp,emile/otp,benoitc/otp-1,release-project/otp,jamesruan/otp,saleyn/otp,platinumthinker/otp,stolen/otp,lucafavatella/otp,isvilen/otp,psyeugenic/otp,electricimp/otp,derek121/otp,cnbin/otp,rlipscombe/otp,lianghaivv/otp,g-andrade/otp,massemanet/otp,kvakvs/otp,enikki/otp,msantos/otp,stolen/otp,benoitc/otp-1,johanclaesson/otp,goertzenator/otp,RichMorin/otp,hairyhum/otp,jemsbhai/otp,lantti/otp,mujiatong/otp,sdebnath/otp,riverrun/otp,saleyn/otp,RGafiyatullin/otp,marquisthunder/otp,paulcager/otp,NOMORECOFFEE/otp,riverrun/otp,lianghaivv/otp,emacsmirror/erlang,palas/otp,RGafiyatullin/otp,weisslj/otp,jamesruan/otp,vic/otp,krishnakumar4a4/otp,bernardd/otp,GinjaNinja32/otp,vladdu/otp,bugs-erlang-org/otp,haguenau/otp,rlipscombe/otp,msantos/otp,GinjaNinja32/otp,vinoski/otp,lucafavatella/otp,emacsmirror/erlang,c-rack/otp,falkevik/otp,yangchengjian/otp,Teino1978-Corp/erlang-otp,jj1bdx/otp,haguenau/otp,benoitc/otp-1,enikki/otp,legoscia/otp,lhslll/otp,emacsmirror/erlang,cnbin/otp,jj1bdx/otp,neeraj9/otp,beni55/otp,electricimp/otp,hairyhum/otp,yangchengjian/otp,jemsbhai/otp,electricimp/otp,g-andrade/otp,vladdu/otp,dgud/otp,marquisthunder/otp,lightcyphers/otp,gjaldon/otp,emile/otp,vinoski/otp,ahmedshafeeq/otp,cnbin/otp,bernardd/otp,RaimoNiskanen/otp,neeraj9/otp,emacsmirror/erlang,lantti/otp,RGafiyatullin/otp,klarna/otp,aboroska/otp,jj1bdx/otp,isvilen/otp,ahmedshafeeq/otp,VincentHHL/otp,dumbbell/otp,mikpe/otp,basho/otp,massemanet/otp,getong/otp,getong/otp,beni55/otp,yangchengjian/otp,basho/otp,neeraj9/otp,neeraj9/otp,falkevik/otp,bernardd/otp,jj1bdx/otp,RGafiyatullin/otp,schlagert/otp,goertzenator/otp,ader1990/otp,Teino1978-Corp/otp,lemenkov/otp,cobusc/otp,vladdu/otp,lianghaivv/otp,lhslll/otp,mikpe/otp,theom/otp,getong/otp,beni55/otp,Teino1978-Corp/erlang-otp,riverrun/otp,jinshana/otp,tuncer/otp,krishnakumar4a4/otp,sammoth-wazoku/otp,bernardd/otp,RJ/otp,bsmr-erlang/otp,g-andrade/otp,schlagert/otp,platinumthinker/otp,sammoth-wazoku/otp,RoadRunnr/otp,ferd/otp,hairyhum/otp,johanclaesson/otp,RaimoNiskanen/otp,bugs-erlang-org/otp,bernardd/otp,isvilen/otp,g-andrade/otp,GinjaNinja32/otp,ferd/otp