IRGen: Allow dynamic class layout for non-ObjC-derived types.
IRGen: Allow dynamic class layout for non-ObjC-derived types.

I checked with David Smith and he says it's been working for him, and we won't find the edge cases till more users hammer on it. ObjC-derived classes however still need some significant runtime interop work.

While we're here, make the 'unimplemented' error message less crashy by just skipping layout of non-fixed fields we can't lay out in ObjC classes yet.

Swift SVN r18797

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