[SILSerializer] keep looking for a SILFunction when we find a declaration.
[SILSerializer] keep looking for a SILFunction when we find a declaration.

It is reasonable that one module has a declaration for a SILFunction while
another module has the definition. We return from lookupSILFunction when
we find a definition and keep looking when a declaration is found from
a module.
 
rdar://16815627


Swift SVN r17586

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