fix isSingleBlockUsage to work in the face of dead code.  It is used to reject obviously broken cases (when an alloc stack has its dealloc_stack in the same block as the allocation, it checks that there are no uses in other blocks) but this isn't correct: uses in dead blocks are fine.  Just ignore them.
fix isSingleBlockUsage to work in the face of dead code.  It is used to reject
obviously broken cases (when an alloc stack has its dealloc_stack in the same block
as the allocation, it checks that there are no uses in other blocks) but this isn't
correct: uses in dead blocks are fine.  Just ignore them.


Swift SVN r24357

ken0nek/swift,LeoShimonaka/swift,IngmarStein/swift,therealbnut/swift,karwa/swift,manavgabhawala/swift,roambotics/swift,harlanhaskins/swift,shajrawi/swift,rudkx/swift,return/swift,zisko/swift,djwbrown/swift,frootloops/swift,gottesmm/swift,kentya6/swift,airspeedswift/swift,SwiftAndroid/swift,JGiola/swift,dduan/swift,allevato/swift,cbrentharris/swift,ken0nek/swift,nathawes/swift,mightydeveloper/swift,MukeshKumarS/Swift,shahmishal/swift,hooman/swift,practicalswift/swift,johnno1962d/swift,arvedviehweger/swift,russbishop/swift,nathawes/swift,bitjammer/swift,rudkx/swift,stephentyrone/swift,kperryua/swift,airspeedswift/swift,jckarter/swift,allevato/swift,sschiau/swift,ben-ng/swift,amraboelela/swift,frootloops/swift,gmilos/swift,natecook1000/swift,slavapestov/swift,ben-ng/swift,djwbrown/swift,xwu/swift,lorentey/swift,modocache/swift,shajrawi/swift,modocache/swift,therealbnut/swift,sdulal/swift,danielmartin/swift,ben-ng/swift,therealbnut/swift,gregomni/swift,shajrawi/swift,tinysun212/swift-windows,roambotics/swift,IngmarStein/swift,Jnosh/swift,mightydeveloper/swift,sdulal/swift,hooman/swift,zisko/swift,jopamer/swift,therealbnut/swift,slavapestov/swift,lorentey/swift,Jnosh/swift,brentdax/swift,atrick/swift,khizkhiz/swift,xedin/swift,kusl/swift,aschwaighofer/swift,swiftix/swift.old,glessard/swift,aschwaighofer/swift,milseman/swift,kentya6/swift,manavgabhawala/swift,tardieu/swift,jtbandes/swift,alblue/swift,deyton/swift,Jnosh/swift,karwa/swift,ken0nek/swift,Ivacker/swift,jtbandes/swift,codestergit/swift,parkera/swift,xwu/swift,tjw/swift,gribozavr/swift,kstaring/swift,aschwaighofer/swift,roambotics/swift,swiftix/swift.old,johnno1962d/swift,practicalswift/swift,djwbrown/swift,hughbe/swift,benlangmuir/swift,xwu/swift,MukeshKumarS/Swift,khizkhiz/swift,swiftix/swift,jopamer/swift,atrick/swift,huonw/swift,felix91gr/swift,Ivacker/swift,mightydeveloper/swift,parkera/swift,alblue/swift,airspeedswift/swift,return/swift,danielmartin/swift,uasys/swift,hughbe/swift,harlanhaskins/swift,mightydeveloper/swift,modocache/swift,harlanhaskins/swift,brentdax/swift,ahoppen/swift,kusl/swift,hooman/swift,devincoughlin/swift,gregomni/swift,sschiau/swift,mightydeveloper/swift,modocache/swift,nathawes/swift,adrfer/swift,tardieu/swift,OscarSwanros/swift,huonw/swift,alblue/swift,deyton/swift,swiftix/swift,LeoShimonaka/swift,zisko/swift,airspeedswift/swift,Jnosh/swift,kentya6/swift,nathawes/swift,lorentey/swift,hughbe/swift,uasys/swift,lorentey/swift,jtbandes/swift,jopamer/swift,russbishop/swift,adrfer/swift,adrfer/swift,danielmartin/swift,danielmartin/swift,dduan/swift,austinzheng/swift,aschwaighofer/swift,sschiau/swift,ben-ng/swift,deyton/swift,jmgc/swift,LeoShimonaka/swift,gregomni/swift,shahmishal/swift,kperryua/swift,apple/swift,brentdax/swift,karwa/swift,shajrawi/swift,jopamer/swift,tkremenek/swift,alblue/swift,xedin/swift,allevato/swift,deyton/swift,dduan/swift,stephentyrone/swift,practicalswift/swift,felix91gr/swift,ahoppen/swift,JGiola/swift,harlanhaskins/swift,CodaFi/swift,zisko/swift,JGiola/swift,slavapestov/swift,tinysun212/swift-windows,uasys/swift,arvedviehweger/swift,swiftix/swift.old,tinysun212/swift-windows,emilstahl/swift,OscarSwanros/swift,apple/swift,shahmishal/swift,JaSpa/swift,emilstahl/swift,devincoughlin/swift,apple/swift,JaSpa/swift,SwiftAndroid/swift,johnno1962d/swift,tkremenek/swift,amraboelela/swift,russbishop/swift,tinysun212/swift-windows,apple/swift,devincoughlin/swift,austinzheng/swift,johnno1962d/swift,KrishMunot/swift,kstaring/swift,lorentey/swift,tardieu/swift,allevato/swift,gottesmm/swift,adrfer/swift,MukeshKumarS/Swift,JGiola/swift,slavapestov/swift,kstaring/swift,kstaring/swift,jckarter/swift,ahoppen/swift,xwu/swift,russbishop/swift,shahmishal/swift,tardieu/swift,emilstahl/swift,khizkhiz/swift,natecook1000/swift,sdulal/swift,benlangmuir/swift,swiftix/swift,sschiau/swift,kperryua/swift,sdulal/swift,xwu/swift,alblue/swift,hooman/swift,nathawes/swift,jckarter/swift,uasys/swift,felix91gr/swift,KrishMunot/swift,JaSpa/swift,airspeedswift/swift,arvedviehweger/swift,lorentey/swift,devincoughlin/swift,kstaring/swift,natecook1000/swift,dduan/swift,OscarSwanros/swift,practicalswift/swift,calebd/swift,sdulal/swift,dduan/swift,gmilos/swift,deyton/swift,cbrentharris/swift,milseman/swift,slavapestov/swift,roambotics/swift,tjw/swift,shajrawi/swift,lorentey/swift,Jnosh/swift,jopamer/swift,shajrawi/swift,jtbandes/swift,JGiola/swift,gribozavr/swift,hooman/swift,Ivacker/swift,gribozavr/swift,gottesmm/swift,devincoughlin/swift,LeoShimonaka/swift,hughbe/swift,brentdax/swift,OscarSwanros/swift,karwa/swift,bitjammer/swift,gribozavr/swift,gribozavr/swift,airspeedswift/swift,frootloops/swift,modocache/swift,huonw/swift,parkera/swift,tinysun212/swift-windows,austinzheng/swift,JaSpa/swift,manavgabhawala/swift,arvedviehweger/swift,atrick/swift,kentya6/swift,jopamer/swift,gmilos/swift,codestergit/swift,aschwaighofer/swift,bitjammer/swift,practicalswift/swift,tkremenek/swift,tjw/swift,kentya6/swift,milseman/swift,sdulal/swift,gottesmm/swift,s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