[ClangImporter] Fix isUnavailableInSwift on non-Apple platforms.
[ClangImporter] Fix isUnavailableInSwift on non-Apple platforms.

Don't bail out early when there's no deprecated-as-unavailable mode;
we also use the loop to check for `availability(swift, unavailable)`.
No test because the only callers are for Objective-C declarations.

tjw/swift,natecook1000/swift,felix91gr/swift,Jnosh/swift,shahmishal/swift,zisko/swift,tinysun212/swift-windows,karwa/swift,airspeedswift/swift,shajrawi/swift,glessard/swift,felix91gr/swift,roambotics/swift,manavgabhawala/swift,djwbrown/swift,jtbandes/swift,milseman/swift,sschiau/swift,gribozavr/swift,parkera/swift,natecook1000/swift,hughbe/swift,manavgabhawala/swift,djwbrown/swift,calebd/swift,amraboelela/swift,ahoppen/swift,frootloops/swift,huonw/swift,arvedviehweger/swift,OscarSwanros/swift,karwa/swift,jmgc/swift,bitjammer/swift,CodaFi/swift,tinysun212/swift-windows,tinysun212/swift-windows,JGiola/swift,aschwaighofer/swift,zisko/swift,frootloops/swift,devincoughlin/swift,practicalswift/swift,Jnosh/swift,danielmartin/swift,tardieu/swift,roambotics/swift,zisko/swift,austinzheng/swift,airspeedswift/swift,return/swift,allevato/swift,stephentyrone/swift,brentdax/swift,CodaFi/swift,harlanhaskins/swift,manavgabhawala/swift,shahmishal/swift,shajrawi/swift,felix91gr/swift,karwa/swift,hooman/swift,zisko/swift,xwu/swift,stephentyrone/swift,xedin/swift,shajrawi/swift,tardieu/swift,frootloops/swift,tkremenek/swift,parkera/swift,felix91gr/swift,Jnosh/swift,gregomni/swift,tinysun212/swift-windows,nathawes/swift,tkremenek/swift,hooman/swift,shahmishal/swift,swiftix/swift,JGiola/swift,swiftix/swift,nathawes/swift,tkremenek/swift,aschwaighofer/swift,bitjammer/swift,gregomni/swift,tinysun212/swift-windows,felix91gr/swift,xedin/swift,aschwaighofer/swift,hooman/swift,jmgc/swift,amraboelela/swift,austinzheng/swift,JGiola/swift,jtbandes/swift,gribozavr/swift,gregomni/swift,deyton/swift,rudkx/swift,jtbandes/swift,xedin/swift,rudkx/swift,harlanhaskins/swift,jopamer/swift,allevato/swift,gribozavr/swift,sschiau/swift,jtbandes/swift,brentdax/swift,sschiau/swift,arvedviehweger/swift,uasys/swift,jopamer/swift,brentdax/swift,milseman/swift,shajrawi/swift,codestergit/swift,gribozavr/swift,djwbrown/swift,roambotics/swift,jmgc/swift,nathawes/swift,glessard/swift,benlangmuir/swift,huonw/swift,parkera/swift,tjw/swift,austinzheng/swift,arvedviehweger/swift,practicalswift/swift,jopamer/swift,jckarter/swift,tjw/swift,swiftix/swift,jtbandes/swift,apple/swift,arvedviehweger/swift,deyton/swift,practicalswift/swift,calebd/swift,aschwaighofer/swift,jmgc/swift,nathawes/swift,tkremenek/swift,tkremenek/swift,shahmishal/swift,austinzheng/swift,brentdax/swift,practicalswift/swift,sschiau/swift,rudkx/swift,ahoppen/swift,roambotics/swift,devincoughlin/swift,airspeedswift/swift,gregomni/swift,deyton/swift,amraboelela/swift,return/swift,devincoughlin/swift,stephentyrone/swift,return/swift,jckarter/swift,amraboelela/swift,xwu/swift,jtbandes/swift,aschwaighofer/swift,hooman/swift,atrick/swift,lorentey/swift,huonw/swift,nathawes/swift,ahoppen/swift,gribozavr/swift,benlangmuir/swift,return/swift,airspeedswift/swift,calebd/swift,CodaFi/swift,natecook1000/swift,milseman/swift,benlangmuir/swift,gribozavr/swift,devincoughlin/swift,shajrawi/swift,gribozavr/swift,jopamer/swift,glessard/swift,alblue/swift,CodaFi/swift,manavgabhawala/swift,djwbrown/swift,jopamer/swift,shahmishal/swift,bitjammer/swift,stephentyrone/swift,hughbe/swift,OscarSwanros/swift,xwu/swift,aschwaighofer/swift,amraboelela/swift,gribozavr/swift,codestergit/swift,austinzheng/swift,huonw/swift,sschiau/swift,Jnosh/swift,codestergit/swift,hughbe/swift,calebd/swift,harlanhaskins/swift,swiftix/swift,milseman/swift,frootloops/swift,nathawes/swift,hughbe/swift,JaSpa/swift,CodaFi/swift,danielmartin/swift,ahoppen/swift,manavgabhawala/swift,danielmartin/swift,austinzheng/swift,frootloops/swift,shahmishal/swift,JaSpa/swift,JaSpa/swift,calebd/swift,arvedviehweger/swift,zisko/swift,sschiau/swift,karwa/swift,danielmartin/swift,OscarSwanros/swift,brentdax/swift,xedin/swift,lorentey/swift,harlanhaskins/swift,Jnosh/swift,tjw/swift,djwbrown/swift,codestergit/swift,alblue/swift,huonw/swift,shajrawi/swift,tjw/swift,glessard/swift,tardieu/swift,Jnosh/swift,CodaFi/swift,arvedviehweger/swift,JaSpa/swift,tkremenek/swift,parkera/swift,allevato/swift,atrick/swift,gregomni/swift,djwbrown/swift,tardieu/swift,amraboelela/swift,frootloops/swift,parkera/swift,deyton/swift,karwa/swift,apple/swift,deyton/swift,shahmishal/swift,huonw/swift,benlangmuir/swift,codestergit/swift,bitjammer/swift,tardieu/swift,tardieu/swift,brentdax/swift,zisko/swift,lorentey/swift,bitjammer/swift,practicalswift/swift,harlanhaskins/swift,JGiola/swift,amraboelela/swift,tinysun212/swift-windows,airspeedswift/swift,austinzheng/swift,natecook1000/swift,tjw/swift,nathawes/swift,gregomni/swift,calebd/swift,hughbe/swift,xwu/swift,return/swift,xedin/swift,jckarter/swift,devincoughlin/swift,airspeedswift/swift,ahoppen/swift,jmgc/swift,sschiau/swift,lorentey/swift,uasys/swift,roambotics/swift,rudkx/swift,Jnosh/swift,alblue/swift,allevato/swift,allevato/swift,harlanhaskins/swift,manavgabhawala/swift,OscarSwanros/swift,milseman/swift,JaSpa/swift,manavgabhawala/swift,sschiau/swift,airspeedswift/swift,karwa/swift,hooman/swift,lorentey/swift,lorentey/swift,jckarter/swift,benlangmuir/swift,OscarSwanros/swift,apple/swift,xwu/swift,JaSpa/swift,alblue/swift,OscarSwanros/swift,deyton/swift,danielmartin/swift,huonw/swift,uasys/swift,glessard/swift,devincoughlin/swift,harlanhaskins/swift,allevato/swift,atrick/swift,practicalswift/swift,xwu/swift,jmgc/swift,jckarter/swift,hooman/swift,ahoppen/swift,apple/swift,xedin/swift,felix91gr/swift,roambotics/swift,glessard/swift,tardieu/swift,hughbe/swift,allevato/swift,arvedviehweger/swift,devincoughlin/swift,jopamer/swift,alblue/swift,swiftix/swift,jtbandes/swift,jckarter/swift,stephentyrone/swift,karwa/swift,danielmartin/swift,milseman/swift,frootloops/swift,stephentyrone/swift,tkremenek/swift,swiftix/swift,JGiola/swift,uasys/swift,hughbe/swift,deyton/swift,alblue/swift,atrick/swift,tinysun212/swift-windows,danielmartin/swift,practicalswift/swift,parkera/swift,xedin/swift,hooman/swift,calebd/swift,felix91gr/swift,lorentey/swift,xedin/swift,atrick/swift,atrick/swift,shahmishal/swift,natecook1000/swift,rudkx/swift,apple/swift,tjw/swift,JaSpa/swift,jckarter/swift,uasys/swift,zisko/swift,OscarSwanros/swift,JGiola/swift,benlangmuir/swift,parkera/swift,apple/swift,devincoughlin/swift,aschwaighofer/swift,codestergit/swift,practicalswift/swift,rudkx/swift,milseman/swift,natecook1000/swift,jopamer/swift,swiftix/swift,CodaFi/swift,bitjammer/swift,karwa/swift,uasys/swift,shajrawi/swift,alblue/swift,natecook1000/swift,djwbrown/swift,jmgc/swift,uasys/swift,xwu/swift,return/swift,parkera/swift,codestergit/swift,stephentyrone/swift,return/swift,shajrawi/swift,bitjammer/swift,lorentey/swift,brentdax/swift