Add a new "swift5-transition" checkout config.
Add a new "swift5-transition" checkout config.

This combination of branches uses the master-llvm-swift5-transition branch
of Swift in combination with the swift-5.0-branch from the LLVM repos.
This will be used on a temporary basis to test Swift with the new LLVM
branches and can be removed when we switch over to develop against the
new LLVM branches by default.

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