stdlib/HashedCollections: don't save the NativeStorage in a local variable
stdlib/HashedCollections: don't save the NativeStorage in a local
variable

We were avoiding recomputing it because it used to be a slow operation.

Performance improvements, as reported by the perf testing buildbot:

Histogram                 -14.07%
StringUtilsUnderscoreCase -10.22%
Dictionary                -10.75%
LevenshteinDistance       -18.08%

Regressions:

* ArraySubscript 8.56%
  This is just bogus.  That test does not do any hashing.

* NSDictionaryCastToSwift 6.86%
  This test does not do any hashing.  It operates only on empty
  dictionaries.  I believe this is noise.

Swift SVN r23991

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