Fix warnings in loadable-types.h.
Fix warnings in loadable-types.h.

The copy and move assignment operators weren't returning anything and
were hence producing "non-void function does not return a value"
warnings.

As the test doesn't actually need a definition for these operators, I've
removed the definition and simply declared them.

apple/swift,nathawes/swift,stephentyrone/swift,roambotics/swift,ahoppen/swift,xwu/swift,gregomni/swift,allevato/swift,apple/swift,roambotics/swift,rudkx/swift,stephentyrone/swift,harlanhaskins/swift,atrick/swift,airspeedswift/swift,parkera/swift,stephentyrone/swift,jckarter/swift,hooman/swift,ahoppen/swift,jmgc/swift,hooman/swift,atrick/swift,jckarter/swift,ahoppen/swift,apple/swift,rudkx/swift,allevato/swift,hooman/swift,glessard/swift,nathawes/swift,roambotics/swift,tkremenek/swift,rudkx/swift,harlanhaskins/swift,JGiola/swift,benlangmuir/swift,rudkx/swift,gregomni/swift,JGiola/swift,apple/swift,nathawes/swift,jmgc/swift,CodaFi/swift,parkera/swift,tkremenek/swift,atrick/swift,apple/swift,benlangmuir/swift,ahoppen/swift,rudkx/swift,gregomni/swift,stephentyrone/swift,allevato/swift,glessard/swift,benlangmuir/swift,hooman/swift,glessard/swift,xwu/swift,allevato/swift,tkremenek/swift,jmgc/swift,nathawes/swift,CodaFi/swift,ahoppen/swift,tkremenek/swift,allevato/swift,glessard/swift,roambotics/swift,nathawes/swift,harlanhaskins/swift,glessard/swift,tkremenek/swift,CodaFi/swift,stephentyrone/swift,JGiola/swift,harlanhaskins/swift,tkremenek/swift,jckarter/swift,jckarter/swift,allevato/swift,CodaFi/swift,parkera/swift,hooman/swift,JGiola/swift,CodaFi/swift,roambotics/swift,harlanhaskins/swift,jckarter/swift,airspeedswift/swift,benlangmuir/swift,parkera/swift,atrick/swift,JGiola/swift,jckarter/swift,rudkx/swift,apple/swift,gregomni/swift,xwu/swift,airspeedswift/swift,parkera/swift,jmgc/swift,stephentyrone/swift,atrick/swift,benlangmuir/swift,glessard/swift,tkremenek/swift,xwu/swift,jckarter/swift,gregomni/swift,parkera/swift,airspeedswift/swift,atrick/swift,CodaFi/swift,harlanhaskins/swift,roambotics/swift,airspeedswift/swift,allevato/swift,xwu/swift,xwu/swift,hooman/swift,nathawes/swift,jmgc/swift,benlangmuir/swift,airspeedswift/swift,parkera/swift,gregomni/swift,jmgc/swift,xwu/swift,parkera/swift,nathawes/swift,stephentyrone/swift,jmgc/swift,ahoppen/swift,hooman/swift,airspeedswift/swift,harlanhaskins/swift,JGiola/swift,CodaFi/swift