Eliminate some warnings while building the stdlib
Eliminate some warnings while building the stdlib

- Move deprecated declarations into a separate deprecated extension
(suppresses tghe warning)
- Mark an initializer from CharacterView as deprecated

Addresses: <rdar://problem/40625231>

jmgc/swift,xwu/swift,harlanhaskins/swift,sschiau/swift,ahoppen/swift,atrick/swift,practicalswift/swift,nathawes/swift,danielmartin/swift,austinzheng/swift,karwa/swift,xedin/swift,apple/swift,apple/swift,karwa/swift,airspeedswift/swift,airspeedswift/swift,amraboelela/swift,airspeedswift/swift,jopamer/swift,brentdax/swift,roambotics/swift,ahoppen/swift,xedin/swift,xedin/swift,xedin/swift,JGiola/swift,nathawes/swift,glessard/swift,amraboelela/swift,brentdax/swift,devincoughlin/swift,harlanhaskins/swift,sschiau/swift,xedin/swift,shajrawi/swift,airspeedswift/swift,jopamer/swift,jmgc/swift,natecook1000/swift,tkremenek/swift,karwa/swift,tkremenek/swift,CodaFi/swift,lorentey/swift,devincoughlin/swift,lorentey/swift,stephentyrone/swift,danielmartin/swift,karwa/swift,alblue/swift,roambotics/swift,rudkx/swift,jopamer/swift,atrick/swift,xwu/swift,shajrawi/swift,atrick/swift,glessard/swift,airspeedswift/swift,austinzheng/swift,glessard/swift,stephentyrone/swift,hooman/swift,stephentyrone/swift,parkera/swift,shajrawi/swift,nathawes/swift,natecook1000/swift,shahmishal/swift,apple/swift,atrick/swift,roambotics/swift,aschwaighofer/swift,gribozavr/swift,hooman/swift,devincoughlin/swift,jckarter/swift,ahoppen/swift,gregomni/swift,apple/swift,jmgc/swift,shahmishal/swift,xwu/swift,devincoughlin/swift,austinzheng/swift,hooman/swift,devincoughlin/swift,allevato/swift,parkera/swift,nathawes/swift,atrick/swift,harlanhaskins/swift,alblue/swift,alblue/swift,benlangmuir/swift,gregomni/swift,lorentey/swift,shajrawi/swift,rudkx/swift,harlanhaskins/swift,sschiau/swift,practicalswift/swift,gribozavr/swift,devincoughlin/swift,xedin/swift,nathawes/swift,apple/swift,benlangmuir/swift,practicalswift/swift,austinzheng/swift,parkera/swift,hooman/swift,jmgc/swift,apple/swift,karwa/swift,jckarter/swift,allevato/swift,allevato/swift,stephentyrone/swift,sschiau/swift,tkremenek/swift,parkera/swift,amraboelela/swift,harlanhaskins/swift,gregomni/swift,harlanhaskins/swift,aschwaighofer/swift,devincoughlin/swift,airspeedswift/swift,gregomni/swift,natecook1000/swift,jckarter/swift,xedin/swift,CodaFi/swift,amraboelela/swift,jopamer/swift,danielmartin/swift,jckarter/swift,xwu/swift,sschiau/swift,JGiola/swift,shajrawi/swift,CodaFi/swift,CodaFi/swift,lorentey/swift,amraboelela/swift,brentdax/swift,shahmishal/swift,practicalswift/swift,glessard/swift,shahmishal/swift,gregomni/swift,gribozavr/swift,danielmartin/swift,roambotics/swift,ahoppen/swift,xwu/swift,rudkx/swift,harlanhaskins/swift,brentdax/swift,jmgc/swift,shajrawi/swift,danielmartin/swift,hooman/swift,gribozavr/swift,karwa/swift,rudkx/swift,roambotics/swift,parkera/swift,jckarter/swift,jckarter/swift,xedin/swift,shajrawi/swift,natecook1000/swift,shajrawi/swift,shahmishal/swift,gribozavr/swift,allevato/swift,allevato/swift,lorentey/swift,parkera/swift,aschwaighofer/swift,austinzheng/swift,benlangmuir/swift,allevato/swift,tkremenek/swift,tkremenek/swift,rudkx/swift,gregomni/swift,JGiola/swift,tkremenek/swift,glessard/swift,practicalswift/swift,practicalswift/swift,parkera/swift,jopamer/swift,brentdax/swift,practicalswift/swift,lorentey/swift,atrick/swift,aschwaighofer/swift,gribozavr/swift,airspeedswift/swift,danielmartin/swift,alblue/swift,jopamer/swift,parkera/swift,stephentyrone/swift,devincoughlin/swift,nathawes/swift,jopamer/swift,ahoppen/swift,natecook1000/swift,shahmishal/swift,sschiau/swift,benlangmuir/swift,aschwaighofer/swift,lorentey/swift,jmgc/swift,sschiau/swift,CodaFi/swift,sschiau/swift,natecook1000/swift,jckarter/swift,karwa/swift,stephentyrone/swift,roambotics/swift,brentdax/swift,JGiola/swift,shahmishal/swift,austinzheng/swift,hooman/swift,austinzheng/swift,amraboelela/swift,glessard/swift,lorentey/swift,CodaFi/swift,allevato/swift,karwa/swift,gribozavr/swift,JGiola/swift,xwu/swift,ahoppen/swift,brentdax/swift,aschwaighofer/swift,xwu/swift,benlangmuir/swift,JGiola/swift,alblue/swift,practicalswift/swift,hooman/swift,nathawes/swift,alblue/swift,amraboelela/swift,benlangmuir/swift,tkremenek/swift,gribozavr/swift,aschwaighofer/swift,natecook1000/swift,shahmishal/swift,rudkx/swift,CodaFi/swift,alblue/swift,jmgc/swift,danielmartin/swift,stephentyrone/swift