Use a cached byte[] preamble for Encoding.UTF8
Use a cached byte[] preamble for Encoding.UTF8

Avoids allocations associated with GetPreamble() for the default and
commonly used Encoding.UTF8 encoding.

twsouthwick/corefx,alexperovich/corefx,tijoytom/corefx,fgreinacher/corefx,dotnet-bot/corefx,tijoytom/corefx,wtgodbe/corefx,rahku/corefx,kkurni/corefx,stephenmichaelf/corefx,lggomez/corefx,weltkante/corefx,Jiayili1/corefx,dsplaisted/corefx,Chrisboh/corefx,billwert/corefx,stone-li/corefx,fgreinacher/corefx,Ermiar/corefx,mafiya69/corefx,jcme/corefx,yizhang82/corefx,ptoonen/corefx,adamralph/corefx,shimingsg/corefx,DnlHarvey/corefx,tijoytom/corefx,seanshpark/corefx,shmao/corefx,Ermiar/corefx,rahku/corefx,zhenlan/corefx,marksmeltzer/corefx,iamjasonp/corefx,cartermp/corefx,benjamin-bader/corefx,iamjasonp/corefx,jlin177/corefx,josguil/corefx,axelheer/corefx,twsouthwick/corefx,mafiya69/corefx,jhendrixMSFT/corefx,rubo/corefx,jlin177/corefx,benjamin-bader/corefx,billwert/corefx,Petermarcu/corefx,nbarbettini/corefx,ellismg/corefx,janhenke/corefx,mokchhya/corefx,cydhaselton/corefx,krytarowski/corefx,alexperovich/corefx,weltkante/corefx,JosephTremoulet/corefx,nchikanov/corefx,dhoehna/corefx,manu-silicon/corefx,parjong/corefx,mokchhya/corefx,jhendrixMSFT/corefx,nbarbettini/corefx,the-dwyer/corefx,dhoehna/corefx,mokchhya/corefx,Priya91/corefx-1,MaggieTsang/corefx,YoupHulsebos/corefx,jcme/corefx,nchikanov/corefx,dotnet-bot/corefx,seanshpark/corefx,jlin177/corefx,pallavit/corefx,jcme/corefx,dhoehna/corefx,ViktorHofer/corefx,shimingsg/corefx,dsplaisted/corefx,benpye/corefx,mafiya69/corefx,mafiya69/corefx,ellismg/corefx,DnlHarvey/corefx,axelheer/corefx,stone-li/corefx,gkhanna79/corefx,jlin177/corefx,yizhang82/corefx,Ermiar/corefx,nbarbettini/corefx,alexperovich/corefx,zhenlan/corefx,shimingsg/corefx,shmao/corefx,iamjasonp/corefx,Ermiar/corefx,MaggieTsang/corefx,Chrisboh/corefx,nbarbettini/corefx,khdang/corefx,rubo/corefx,alphonsekurian/corefx,ptoonen/corefx,jcme/corefx,mazong1123/corefx,billwert/corefx,Ermiar/corefx,billwert/corefx,parjong/corefx,marksmeltzer/corefx,krk/corefx,ericstj/corefx,jcme/corefx,krytarowski/corefx,nchikanov/corefx,alphonsekurian/corefx,SGuyGe/corefx,MaggieTsang/corefx,Priya91/corefx-1,ViktorHofer/corefx,josguil/corefx,iamjasonp/corefx,jhendrixMSFT/corefx,Priya91/corefx-1,cartermp/corefx,rahku/corefx,tijoytom/corefx,ptoonen/corefx,krytarowski/corefx,wtgodbe/corefx,seanshpark/corefx,mmitche/corefx,gkhanna79/corefx,manu-silicon/corefx,ericstj/corefx,weltkante/corefx,nchikanov/corefx,dotnet-bot/corefx,cydhaselton/corefx,mmitche/corefx,ptoonen/corefx,stephenmichaelf/corefx,DnlHarvey/corefx,alphonsekurian/corefx,manu-silicon/corefx,tstringer/corefx,yizhang82/corefx,BrennanConroy/corefx,shmao/corefx,stephenmichaelf/corefx,mazong1123/corefx,mellinoe/corefx,ericstj/corefx,ravimeda/corefx,kkurni/corefx,zhenlan/corefx,rubo/corefx,JosephTremoulet/corefx,elijah6/corefx,krk/corefx,marksmeltzer/corefx,MaggieTsang/corefx,nbarbettini/corefx,the-dwyer/corefx,axelheer/corefx,Chrisboh/corefx,janhenke/corefx,tstringer/corefx,shimingsg/corefx,wtgodbe/corefx,Ermiar/corefx,ravimeda/corefx,stone-li/corefx,richlander/corefx,alphonsekurian/corefx,cartermp/corefx,gkhanna79/corefx,Priya91/corefx-1,elijah6/corefx,yizhang82/corefx,kkurni/corefx,ellismg/corefx,yizhang82/corefx,jhendrixMSFT/corefx,cydhaselton/corefx,richlander/corefx,khdang/corefx,Chrisboh/corefx,SGuyGe/corefx,BrennanConroy/corefx,ericstj/corefx,krytarowski/corefx,ravimeda/corefx,rubo/corefx,kkurni/corefx,pallavit/corefx,YoupHulsebos/corefx,khdang/corefx,benpye/corefx,ViktorHofer/corefx,cartermp/corefx,Jiayili1/corefx,rjxby/corefx,rjxby/corefx,weltkante/corefx,weltkante/corefx,janhenke/corefx,cartermp/corefx,JosephTremoulet/corefx,Petermarcu/corefx,YoupHulsebos/corefx,ViktorHofer/corefx,mazong1123/corefx,richlander/corefx,lggomez/corefx,DnlHarvey/corefx,krk/corefx,pallavit/corefx,ravimeda/corefx,kkurni/corefx,benpye/corefx,ptoonen/corefx,twsouthwick/corefx,rjxby/corefx,tstringer/corefx,yizhang82/corefx,elijah6/corefx,shimingsg/corefx,mmitche/corefx,billwert/corefx,benjamin-bader/corefx,benpye/corefx,alexperovich/corefx,alexperovich/corefx,alexperovich/corefx,dotnet-bot/corefx,iamjasonp/corefx,tstringer/corefx,mafiya69/corefx,janhenke/corefx,gkhanna79/corefx,jlin177/corefx,DnlHarvey/corefx,rahku/corefx,Petermarcu/corefx,tijoytom/corefx,Priya91/corefx-1,parjong/corefx,billwert/corefx,mokchhya/corefx,SGuyGe/corefx,mokchhya/corefx,YoupHulsebos/corefx,alphonsekurian/corefx,benjamin-bader/corefx,Petermarcu/corefx,Jiayili1/corefx,Petermarcu/corefx,wtgodbe/corefx,mellinoe/corefx,jhendrixMSFT/corefx,seanshpark/corefx,ViktorHofer/corefx,rjxby/corefx,elijah6/corefx,SGuyGe/corefx,stephenmichaelf/corefx,axelheer/corefx,ptoonen/corefx,mafiya69/corefx,krytarowski/corefx,richlander/corefx,stephenmichaelf/corefx,wtgodbe/corefx,mokchhya/corefx,krk/corefx,billwert/corefx,mazong1123/corefx,shimingsg/corefx,stephenmichaelf/corefx,dsplaisted/corefx,josguil/corefx,cartermp/corefx,ViktorHofer/corefx,Petermarcu/corefx,alexperovich/corefx,mazong1123/corefx,rjxby/corefx,weltkante/corefx,the-dwyer/corefx,dhoehna/corefx,weltkante/corefx,shahid-pk/corefx,the-dwyer/corefx,parjong/corefx,fgreinacher/corefx,MaggieTsang/corefx,zhenlan/corefx,BrennanConroy/corefx,nbarbettini/corefx,benjamin-bader/corefx,mazong1123/corefx,twsouthwick/corefx,twsouthwick/corefx,elijah6/corefx,ravimeda/corefx,wtgodbe/corefx,Ermiar/corefx,manu-silicon/corefx,marksmeltzer/corefx,richlander/corefx,YoupHulsebos/corefx,seanshpark/corefx,marksmeltzer/corefx,shahid-pk/corefx,tstringer/corefx,alphonsekurian/corefx,SGuyGe/corefx,nchikanov/corefx,ericstj/corefx,pallavit/corefx,elijah6/corefx,mellinoe/corefx,nchikanov/corefx,josguil/corefx,twsouthwick/corefx,shmao/corefx,mmitche/corefx,dhoehna/corefx,ellismg/corefx,stone-li/corefx,shahid-pk/corefx,ViktorHofer/corefx,mmitche/corefx,parjong/corefx,Chrisboh/corefx,manu-silicon/corefx,rahku/corefx,yizhang82/corefx,shmao/corefx,JosephTremoulet/corefx,lggomez/corefx,elijah6/corefx,MaggieTsang/corefx,JosephTremoulet/corefx,lggomez/corefx,ellismg/corefx,adamralph/corefx,rubo/corefx,parjong/corefx,mazong1123/corefx,gkhanna79/corefx,jcme/corefx,YoupHulsebos/corefx,ericstj/corefx,shahid-pk/corefx,the-dwyer/corefx,gkhanna79/corefx,ericstj/corefx,nbarbettini/corefx,Jiayili1/corefx,iamjasonp/corefx,DnlHarvey/corefx,benpye/corefx,shahid-pk/corefx,jhendrixMSFT/corefx,jlin177/corefx,khdang/corefx,fgreinacher/corefx,parjong/corefx,the-dwyer/corefx,janhenke/corefx,richlander/corefx,cydhaselton/corefx,the-dwyer/corefx,mellinoe/corefx,lggomez/corefx,dhoehna/corefx,marksmeltzer/corefx,shmao/corefx,iamjasonp/corefx,JosephTremoulet/corefx,lggomez/corefx,wtgodbe/corefx,pallavit/corefx,dotnet-bot/corefx,twsouthwick/corefx,kkurni/corefx,DnlHarvey/corefx,stone-li/corefx,tijoytom/corefx,krk/corefx,marksmeltzer/corefx,manu-silicon/corefx,khdang/corefx,ptoonen/corefx,dhoehna/corefx,ellismg/corefx,YoupHulsebos/corefx,mellinoe/corefx,khdang/corefx,Jiayili1/corefx,krytarowski/corefx,stone-li/corefx,seanshpark/corefx,gkhanna79/corefx,jlin177/corefx,mmitche/corefx,MaggieTsang/corefx,shimingsg/corefx,dotnet-bot/corefx,benjamin-bader/corefx,SGuyGe/corefx,ravimeda/corefx,stone-li/corefx,zhenlan/corefx,krytarowski/corefx,Priya91/corefx-1,lggomez/corefx,Jiayili1/corefx,alphonsekurian/corefx,nchikanov/corefx,tijoytom/corefx,josguil/corefx,tstringer/corefx,Jiayili1/corefx,Petermarcu/corefx,mellinoe/corefx,josguil/corefx,adamralph/corefx,richlander/corefx,manu-silicon/corefx,rjxby/corefx,jhendrixMSFT/corefx,janhenke/corefx,rjxby/corefx,shahid-pk/corefx,axelheer/corefx,dotnet-bot/corefx,shmao/corefx,cydhaselton/corefx,zhenlan/corefx,ravimeda/corefx,axelheer/corefx,stephenmichaelf/corefx,seanshpark/corefx,cydhaselton/corefx,benpye/corefx,rahku/corefx,zhenlan/corefx,cydhaselton/corefx,rahku/corefx,pallavit/corefx,JosephTremoulet/corefx,Chrisboh/corefx,mmitche/corefx,krk/corefx,krk/corefx