[sil-devirtualizer] Add a helper function to compute all subclasses of a given class.
[sil-devirtualizer] Add a helper function to compute all subclasses of a given class.

The new function uses the ClassHierarchyAnalysis to do its job.

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