added support of let statements and base support of block scoping for identifiers, cf #883
added support of let statements and base support of block scoping for identifiers, cf #883

aisk/jshint,jugglinmike/jshint,niedzielski/jshint,Endika/jshint,davidjb/jshint,alivesay/jshint,paul-wade/jshint,pansay/jshint,scottsmeester/jshint,jshint/jshint,stevemao/jshint,nicolo-ribaudo/jshint,ecomfe/edp-jshint,wzup/jshint,llucbrell/jshint,jonnyreeves/jshint,mohsen1/jshint,Joy603/jshint,shreyasgaonkar/jshint,raix/jshint,kangax/jshint,paladox/jshint,jugglinmike/jshint,luisbrito/jshint,lukeapage/jshint,fashionsun/jshint,zynick/jshint,nicolo-ribaudo/jshint,pansay/jshint,mcanthony/jshint,behind2/jshint,AndriiGro/jshint,yyx990803/jshint,elkingtonmcb/jshint,supriyantomaftuh/jshint,lovemeblender/jshint,max789/jshint,yadimon/jshint,wzup/jshint,jagdeesh109/jshint,louwers/jshint,cnbin/jshint,beni55/jshint,luisbrito/jshint,llucbrell/jshint,mrjoelkemp/jshint,alivesay/jshint,Joy603/jshint,doggy8088/jshint,BridgeAR/jshint,laurensortiz/jshint,AndriiGro/jshint,silverwind/jshint,aisk/jshint,BridgeAR/jshint,wisavalite/jshint,fashionsun/jshint,thomas658/jshint,rwaldron/jshint,meh-uk/jshint,n8io/jshint,mohsen1/jshint,mrjoelkemp/jshint,davidjb/jshint,supriyantomaftuh/jshint,nitinlal/jshint,gtanner/jshint,freeyiyi1993/jshint,beni55/jshint,marian-r/jshint,wisavalite/jshint,paul-wade/jshint,thomas658/jshint,paragag/AntiRedis,kidaa/jshint,max789/jshint,niedzielski/jshint,behind2/jshint,jagdeesh109/jshint,kidaa/jshint,laurensortiz/jshint,yadimon/jshint,jshint/jshint,shreyasgaonkar/jshint,n8io/jshint,louwers/jshint,ljharb/jshint,Endika/jshint,gloryknight/jshint,freeyiyi1993/jshint,crivas/jshint,ljharb/jshint,cnbin/jshint,stevemao/jshint,fairfieldt/jshint,nitinlal/jshint,ThiagoGarciaAlves/jshint,SqrTT/dwhint,Jeremy017/jshint,gameclosure/jsiohint,marian-r/jshint,gtanner/jshint,Jeremy017/jshint,ghtest712/bearded-octo-dangerzone,darongE/jshint,Khan/jshint,lukeapage/jshint,crivas/jshint,mcanthony/jshint,elkingtonmcb/jshint,scottsmeester/jshint,doggy8088/jshint