Replace "optVal = Nothing" with "optVal.reset()" for Optional<ArrayRef<T>>.
Replace "optVal = Nothing" with "optVal.reset()" for Optional<ArrayRef<T>>.

In preparation for the switch to llvm::Optional, which is constructible from
the same dummy llvm::NoneType as llvm::ArrayRef, making the assignment
ambiguous.

Swift SVN r22473

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