Support a :&catch argument for start() and Promise.start()
Support a :&catch argument for start() and Promise.start()

This allows timely detection of exceptions thrown by tasks
that may not be await'ed for some time (e.g. because they
are background tasks not expected to complete for a long time),
and mirrors the same parameter on ThreadPoolScheduler.cue().

Leont/rakudo,azawawi/rakudo,ugexe/rakudo,labster/rakudo,awwaiid/rakudo,LLFourn/rakudo,LLFourn/rakudo,Gnouc/rakudo,cygx/rakudo,Leont/rakudo,ugexe/rakudo,nbrown/rakudo,ab5tract/rakudo,LLFourn/rakudo,tony-o/rakudo,tbrowder/rakudo,samcv/rakudo,tbrowder/rakudo,zostay/rakudo,nunorc/rakudo,lucasbuchala/rakudo,salortiz/rakudo,usev6/rakudo,sergot/rakudo,b2gills/rakudo,labster/rakudo,ab5tract/rakudo,rakudo/rakudo,Leont/rakudo,usev6/rakudo,b2gills/rakudo,laben/rakudo,zhuomingliang/rakudo,cognominal/rakudo,Gnouc/rakudo,jonathanstowe/rakudo,b2gills/rakudo,niner/rakudo,sjn/rakudo,tony-o/deb-rakudodaily,skids/rakudo,tony-o/rakudo,softmoth/rakudo,Gnouc/rakudo,skids/rakudo,laben/rakudo,sjn/rakudo,tony-o/rakudo,labster/rakudo,azawawi/rakudo,cognominal/rakudo,softmoth/rakudo,sjn/rakudo,dankogai/rakudo,nbrown/rakudo,tony-o/rakudo,ab5tract/rakudo,tony-o/deb-rakudodaily,b2gills/rakudo,azawawi/rakudo,sjn/rakudo,softmoth/rakudo,tony-o/rakudo,jonathanstowe/rakudo,raydiak/rakudo,rakudo/rakudo,skids/rakudo,nbrown/rakudo,labster/rakudo,MasterDuke17/rakudo,paultcochrane/rakudo,rakudo/rakudo,tbrowder/rakudo,softmoth/rakudo,nbrown/rakudo,paultcochrane/rakudo,ungrim97/rakudo,usev6/rakudo,MasterDuke17/rakudo,cognominal/rakudo,Gnouc/rakudo,cognominal/rakudo,zhuomingliang/rakudo,tony-o/deb-rakudodaily,niner/rakudo,cognominal/rakudo,skids/rakudo,zostay/rakudo,tbrowder/rakudo,nbrown/rakudo,lucasbuchala/rakudo,lucasbuchala/rakudo,zostay/rakudo,Leont/rakudo,rakudo/rakudo,salortiz/rakudo,awwaiid/rakudo,dankogai/rakudo,jonathanstowe/rakudo,niner/rakudo,usev6/rakudo,paultcochrane/rakudo,ab5tract/rakudo,paultcochrane/rakudo,sjn/rakudo,tbrowder/rakudo,LLFourn/rakudo,laben/rakudo,Gnouc/rakudo,cygx/rakudo,ugexe/rakudo,nunorc/rakudo,tony-o/deb-rakudodaily,zhuomingliang/rakudo,usev6/rakudo,b2gills/rakudo,laben/rakudo,dankogai/rakudo,labster/rakudo,ungrim97/rakudo,ungrim97/rakudo,rakudo/rakudo,Gnouc/rakudo,sergot/rakudo,salortiz/rakudo,samcv/rakudo,zostay/rakudo,cygx/rakudo,sergot/rakudo,nunorc/rakudo,dankogai/rakudo,MasterDuke17/rakudo,samcv/rakudo,tony-o/deb-rakudodaily,raydiak/rakudo,jonathanstowe/rakudo,awwaiid/rakudo,cygx/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,ab5tract/rakudo,salortiz/rakudo,labster/rakudo,niner/rakudo,ugexe/rakudo,awwaiid/rakudo,tony-o/deb-rakudodaily,salortiz/rakudo,MasterDuke17/rakudo,raydiak/rakudo,salortiz/rakudo,rakudo/rakudo,samcv/rakudo,LLFourn/rakudo,ungrim97/rakudo,MasterDuke17/rakudo,awwaiid/rakudo,samcv/rakudo,azawawi/rakudo,MasterDuke17/rakudo,skids/rakudo,paultcochrane/rakudo,ungrim97/rakudo,azawawi/rakudo,tony-o/rakudo,tony-o/deb-rakudodaily,softmoth/rakudo,dankogai/rakudo,sergot/rakudo,nbrown/rakudo,lucasbuchala/rakudo,jonathanstowe/rakudo,zhuomingliang/rakudo,cygx/rakudo,ugexe/rakudo,raydiak/rakudo,nunorc/rakudo