Add test of warnings for assignments in conditionals.
Add test of warnings for assignments in conditionals.

- Only the last expression of a comma expression will trigger the
  warning.
- Parens around the entire comma expression will prevent the warning.
- Parens around the assignment expression will prevent the warning.

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