[RemoteAST] Fix typo in existential payload calculation.
[RemoteAST] Fix typo in existential payload calculation.

This only shows up in lldb, so I'm adding a test there and
test the two commits together.

xedin/swift,shahmishal/swift,xwu/swift,stephentyrone/swift,CodaFi/swift,danielmartin/swift,lorentey/swift,airspeedswift/swift,gribozavr/swift,xedin/swift,jmgc/swift,danielmartin/swift,gribozavr/swift,JGiola/swift,roambotics/swift,rudkx/swift,karwa/swift,benlangmuir/swift,tkremenek/swift,devincoughlin/swift,alblue/swift,xedin/swift,apple/swift,danielmartin/swift,apple/swift,alblue/swift,atrick/swift,atrick/swift,roambotics/swift,danielmartin/swift,aschwaighofer/swift,gregomni/swift,jmgc/swift,ahoppen/swift,nathawes/swift,harlanhaskins/swift,austinzheng/swift,austinzheng/swift,JGiola/swift,devincoughlin/swift,glessard/swift,stephentyrone/swift,shajrawi/swift,shahmishal/swift,austinzheng/swift,aschwaighofer/swift,JGiola/swift,xedin/swift,tkremenek/swift,devincoughlin/swift,ahoppen/swift,austinzheng/swift,sschiau/swift,aschwaighofer/swift,karwa/swift,hooman/swift,xwu/swift,parkera/swift,aschwaighofer/swift,jckarter/swift,gribozavr/swift,shahmishal/swift,hooman/swift,apple/swift,lorentey/swift,gribozavr/swift,jmgc/swift,jmgc/swift,stephentyrone/swift,karwa/swift,xwu/swift,hooman/swift,sschiau/swift,airspeedswift/swift,alblue/swift,rudkx/swift,parkera/swift,shahmishal/swift,amraboelela/swift,aschwaighofer/swift,devincoughlin/swift,jckarter/swift,airspeedswift/swift,tkremenek/swift,airspeedswift/swift,roambotics/swift,airspeedswift/swift,practicalswift/swift,shajrawi/swift,xedin/swift,practicalswift/swift,CodaFi/swift,nathawes/swift,gregomni/swift,airspeedswift/swift,rudkx/swift,harlanhaskins/swift,lorentey/swift,atrick/swift,stephentyrone/swift,practicalswift/swift,harlanhaskins/swift,atrick/swift,jckarter/swift,sschiau/swift,devincoughlin/swift,CodaFi/swift,hooman/swift,sschiau/swift,atrick/swift,jckarter/swift,xedin/swift,atrick/swift,shajrawi/swift,shajrawi/swift,amraboelela/swift,hooman/swift,hooman/swift,lorentey/swift,xedin/swift,shahmishal/swift,rudkx/swift,practicalswift/swift,tkremenek/swift,shahmishal/swift,parkera/swift,jmgc/swift,danielmartin/swift,gribozavr/swift,amraboelela/swift,benlangmuir/swift,karwa/swift,glessard/swift,allevato/swift,alblue/swift,stephentyrone/swift,allevato/swift,roambotics/swift,parkera/swift,amraboelela/swift,shajrawi/swift,aschwaighofer/swift,hooman/swift,xwu/swift,karwa/swift,practicalswift/swift,rudkx/swift,austinzheng/swift,shajrawi/swift,gregomni/swift,gribozavr/swift,practicalswift/swift,benlangmuir/swift,CodaFi/swift,harlanhaskins/swift,lorentey/swift,shajrawi/swift,allevato/swift,harlanhaskins/swift,sschiau/swift,ahoppen/swift,lorentey/swift,gregomni/swift,devincoughlin/swift,gregomni/swift,practicalswift/swift,CodaFi/swift,parkera/swift,jckarter/swift,amraboelela/swift,alblue/swift,nathawes/swift,nathawes/swift,jmgc/swift,JGiola/swift,apple/swift,glessard/swift,rudkx/swift,lorentey/swift,austinzheng/swift,gribozavr/swift,harlanhaskins/swift,tkremenek/swift,tkremenek/swift,xwu/swift,karwa/swift,devincoughlin/swift,shajrawi/swift,devincoughlin/swift,glessard/swift,ahoppen/swift,benlangmuir/swift,sschiau/swift,ahoppen/swift,CodaFi/swift,amraboelela/swift,alblue/swift,gregomni/swift,danielmartin/swift,allevato/swift,gribozavr/swift,nathawes/swift,apple/swift,airspeedswift/swift,harlanhaskins/swift,jckarter/swift,allevato/swift,austinzheng/swift,aschwaighofer/swift,sschiau/swift,xwu/swift,apple/swift,jmgc/swift,CodaFi/swift,JGiola/swift,jckarter/swift,xedin/swift,glessard/swift,parkera/swift,JGiola/swift,benlangmuir/swift,amraboelela/swift,stephentyrone/swift,stephentyrone/swift,nathawes/swift,shahmishal/swift,tkremenek/swift,danielmartin/swift,karwa/swift,allevato/swift,karwa/swift,nathawes/swift,allevato/swift,glessard/swift,sschiau/swift,parkera/swift,lorentey/swift,alblue/swift,roambotics/swift,roambotics/swift,benlangmuir/swift,ahoppen/swift,xwu/swift,parkera/swift,practicalswift/swift,shahmishal/swift