FrontendInputs data structure redo.
FrontendInputs data structure redo.

- Outlaw duplicate input files, fix driver, fix tests, and add test.
- Reflect that no buffer is present without a (possibly pseudo) named file.
- Reflect fact that every input has a (possible pseudo) name.
- Break up CompilerInstance::setup.
-

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