[stdlib] ExistentialCollection: use -> Self where possible
[stdlib] ExistentialCollection: use -> Self where possible

<rdar://20181253> prevents using it everywhere we should, but it's a start

Swift SVN r26211

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