[ClangImporter] Don't try to load things if there's been a fatal Clang error.
[ClangImporter] Don't try to load things if there's been a fatal Clang error.

This should help us avoid crashes like rdar://problem/19798049 in the future.
Of course, since fatal errors are so rare, I don't have a way to test this,
but it isn't breaking any of the paths we currently use.

rdar://problem/19827938

Swift SVN r25285

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