Strengthen and clarify the assertions in swift_release and swift_unpin.
Strengthen and clarify the assertions in
swift_release and swift_unpin.

Swift SVN r24422

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