Better "JavaScript evaluation error" message
Better "JavaScript evaluation error" message

Less's messages for JavaScript evaluation errors do not contain the actual error thrown, making them very hard to debug. This PR adds the error message to the log.
deciament/less.js,featurist/less-vars,demohi/less.js,PUSEN/less.js,wjb12/less.js,deciament/less.js,huzion/less.js,dyx/less.js,arusanov/less.js,ahstro/less.js,NaSymbol/less.js,mcanthony/less.js,arusanov/less.js,miguel-serrano/less.js,thinkDevDM/less.js,SkReD/less.js,xiaoyanit/less.js,wyfyyy818818/less.js,sqliang/less.js,angeliaz/less.js,jdan/less.js,thinkDevDM/less.js,bendroid/less.js,bammoo/less.js,chenxiaoxing1992/less.js,wyfyyy818818/less.js,aichangzhi123/less.js,mishal/less.js,PUSEN/less.js,yuhualingfeng/less.js,dyx/less.js,seven-phases-max/less.js,sqliang/less.js,MrChen2015/less.js,nolanlawson/less.js,miguel-serrano/less.js,lvpeng/less.js,waiter/less.js,less/less.js,evocateur/less.js,bhavyaNaveen/project1,foresthz/less.js,ridixcr/less.js,telerik/less.js,bendroid/less.js,NirViaje/less.js,idreamingreen/less.js,egg-/less.js,yuhualingfeng/less.js,waiter/less.js,christer155/less.js,mtscout6/less.js,featurist/less-vars,SomMeri/less-rhino.js,paladox/less.js,jjj117/less.js,NaSymbol/less.js,jdan/less.js,cgvarela/less.js,angeliaz/less.js,ahutchings/less.js,paladox/less.js,Synchro/less.js,ridixcr/less.js,Nastarani1368/less.js,cypher0x9/less.js,huzion/less.js,telerik/less.js,pkdevbox/less.js,seven-phases-max/less.js,christer155/less.js,royriojas/less.js,ahutchings/less.js,gencer/less.js,SkReD/less.js,foresthz/less.js,gencer/less.js,egg-/less.js,ahstro/less.js,lincome/less.js,MrChen2015/less.js,aichangzhi123/less.js,SomMeri/less-rhino.js,jjj117/less.js,chenxiaoxing1992/less.js,bammoo/less.js,cgvarela/less.js,wjb12/less.js,Synchro/less.js,mcanthony/less.js,evocateur/less.js,xiaoyanit/less.js,royriojas/less.js,HossainKhademian/LessJs,demohi/less.js,nolanlawson/less.js,idreamingreen/less.js,less/less.js,cypher0x9/less.js,AlexMeliq/less.js,lvpeng/less.js,pkdevbox/less.js,less/less.js,mishal/less.js,bhavyaNaveen/project1,lincome/less.js,AlexMeliq/less.js,Nastarani1368/less.js,NirViaje/less.js