util: Make the number of app units per pixel a constant instead of repeating the literal value everywhere.
util: Make the number of app units per pixel a constant instead of
repeating the literal value everywhere.

Factoring this value out into a public constant makes it easier to
create `Au` constants in other modules.

saneyuki/servo,DominoTree/servo,saneyuki/servo,splav/servo,jimberlage/servo,eddyb/servo,brendandahl/servo,emilio/servo,pyfisch/servo,larsbergstrom/servo,avadacatavra/servo,splav/servo,peterjoel/servo,SimonSapin/servo,emilio/servo,runarberg/servo,mbrubeck/servo,brendandahl/servo,rnestler/servo,dati91/servo,KiChjang/servo,j3parker/servo,notriddle/servo,mattnenterprise/servo,nnethercote/servo,szeged/servo,ConnorGBrewster/servo,mbrubeck/servo,dsandeephegde/servo,peterjoel/servo,pyfisch/servo,fiji-flo/servo,fiji-flo/servo,DominoTree/servo,sadmansk/servo,paulrouget/servo,GyrosOfWar/servo,upsuper/servo,dsandeephegde/servo,sadmansk/servo,ConnorGBrewster/servo,mattnenterprise/servo,anthgur/servo,ConnorGBrewster/servo,SimonSapin/servo,cbrewster/servo,larsbergstrom/servo,rnestler/servo,ConnorGBrewster/servo,peterjoel/servo,szeged/servo,anthgur/servo,nrc/servo,thiagopnts/servo,anthgur/servo,notriddle/servo,dati91/servo,nnethercote/servo,pyfisch/servo,canaltinova/servo,szeged/servo,brendandahl/servo,KiChjang/servo,thiagopnts/servo,cbrewster/servo,pyfisch/servo,runarberg/servo,j3parker/servo,fiji-flo/servo,ConnorGBrewster/servo,RenaudParis/servo,canaltinova/servo,dati91/servo,cbrewster/servo,CJ8664/servo,paulrouget/servo,steveklabnik/servo,szeged/servo,notriddle/servo,dsandeephegde/servo,mbrubeck/servo,cbrewster/servo,AnthonyBroadCrawford/servo,CJ8664/servo,saneyuki/servo,notriddle/servo,AnthonyBroadCrawford/servo,CJ8664/servo,upsuper/servo,upsuper/servo,steveklabnik/servo,pyfisch/servo,KiChjang/servo,splav/servo,jimberlage/servo,runarberg/servo,runarberg/servo,j3parker/servo,jimberlage/servo,nnethercote/servo,paulrouget/servo,GyrosOfWar/servo,nnethercote/servo,fiji-flo/servo,GyrosOfWar/servo,emilio/servo,dagnir/servo,avadacatavra/servo,anthgur/servo,szeged/servo,larsbergstrom/servo,fiji-flo/servo,thiagopnts/servo,dati91/servo,mattnenterprise/servo,anthgur/servo,SimonSapin/servo,SimonSapin/servo,cbrewster/servo,eddyb/servo,splav/servo,bjwbell/servo,nrc/servo,AnthonyBroadCrawford/servo,steveklabnik/servo,dsandeephegde/servo,mbrubeck/servo,bjwbell/servo,RenaudParis/servo,szeged/servo,eddyb/servo,dagnir/servo,szeged/servo,saneyuki/servo,dagnir/servo,nnethercote/servo,splav/servo,CJ8664/servo,splav/servo,saneyuki/servo,emilio/servo,pyfisch/servo,RenaudParis/servo,larsbergstrom/servo,DominoTree/servo,notriddle/servo,upsuper/servo,runarberg/servo,GyrosOfWar/servo,szeged/servo,nrc/servo,rnestler/servo,thiagopnts/servo,brendandahl/servo,mattnenterprise/servo,larsbergstrom/servo,canaltinova/servo,KiChjang/servo,DominoTree/servo,GyrosOfWar/servo,canaltinova/servo,ConnorGBrewster/servo,peterjoel/servo,pyfisch/servo,emilio/servo,splav/servo,GyrosOfWar/servo,saneyuki/servo,KiChjang/servo,bjwbell/servo,sadmansk/servo,DominoTree/servo,fiji-flo/servo,avadacatavra/servo,avadacatavra/servo,peterjoel/servo,KiChjang/servo,rnestler/servo,larsbergstrom/servo,nnethercote/servo,rnestler/servo,dati91/servo,brendandahl/servo,larsbergstrom/servo,jimberlage/servo,thiagopnts/servo,larsbergstrom/servo,eddyb/servo,peterjoel/servo,KiChjang/servo,dsandeephegde/servo,canaltinova/servo,SimonSapin/servo,saneyuki/servo,avadacatavra/servo,paulrouget/servo,szeged/servo,mbrubeck/servo,peterjoel/servo,dati91/servo,upsuper/servo,nnethercote/servo,szeged/servo,bjwbell/servo,CJ8664/servo,paulrouget/servo,RenaudParis/servo,notriddle/servo,emilio/servo,peterjoel/servo,cbrewster/servo,RenaudParis/servo,anthgur/servo,DominoTree/servo,AnthonyBroadCrawford/servo,emilio/servo,dsandeephegde/servo,mattnenterprise/servo,CJ8664/servo,emilio/servo,sadmansk/servo,sadmansk/servo,avadacatavra/servo,thiagopnts/servo,runarberg/servo,DominoTree/servo,nrc/servo,paulrouget/servo,nnethercote/servo,mattnenterprise/servo,runarberg/servo,nnethercote/servo,KiChjang/servo,KiChjang/servo,DominoTree/servo,rnestler/servo,RenaudParis/servo,AnthonyBroadCrawford/servo,steveklabnik/servo,jimberlage/servo,anthgur/servo,CJ8664/servo,steveklabnik/servo,eddyb/servo,fiji-flo/servo,j3parker/servo,brendandahl/servo,eddyb/servo,brendandahl/servo,pyfisch/servo,eddyb/servo,mbrubeck/servo,canaltinova/servo,saneyuki/servo,nrc/servo,nrc/servo,peterjoel/servo,fiji-flo/servo,dagnir/servo,dati91/servo,nrc/servo,mbrubeck/servo,DominoTree/servo,splav/servo,sadmansk/servo,j3parker/servo,dati91/servo,paulrouget/servo,upsuper/servo,upsuper/servo,cbrewster/servo,paulrouget/servo,jimberlage/servo,paulrouget/servo,paulrouget/servo,bjwbell/servo,SimonSapin/servo,rnestler/servo,jimberlage/servo,jimberlage/servo,thiagopnts/servo,SimonSapin/servo,anthgur/servo,dagnir/servo,KiChjang/servo,AnthonyBroadCrawford/servo,CJ8664/servo,saneyuki/servo,steveklabnik/servo,ConnorGBrewster/servo,j3parker/servo,eddyb/servo,SimonSapin/servo,larsbergstrom/servo,sadmansk/servo,splav/servo,larsbergstrom/servo,canaltinova/servo,upsuper/servo,nnethercote/servo,pyfisch/servo,avadacatavra/servo,thiagopnts/servo,avadacatavra/servo,peterjoel/servo,bjwbell/servo,emilio/servo,GyrosOfWar/servo,canaltinova/servo,saneyuki/servo,splav/servo,emilio/servo,dagnir/servo,mbrubeck/servo,dsandeephegde/servo,steveklabnik/servo,mattnenterprise/servo,DominoTree/servo,cbrewster/servo,j3parker/servo,pyfisch/servo,bjwbell/servo,rnestler/servo,RenaudParis/servo,jimberlage/servo,mattnenterprise/servo,sadmansk/servo,AnthonyBroadCrawford/servo,notriddle/servo,notriddle/servo,notriddle/servo,dsandeephegde/servo,notriddle/servo,ConnorGBrewster/servo,dagnir/servo