[libswift] Update SWIFT_IMPORT_REFERENCE to use import_reference.
[libswift] Update SWIFT_IMPORT_REFERENCE to use import_reference.

roambotics/swift,JGiola/swift,JGiola/swift,roambotics/swift,roambotics/swift,JGiola/swift,apple/swift,glessard/swift,roambotics/swift,benlangmuir/swift,glessard/swift,apple/swift,apple/swift,benlangmuir/swift,glessard/swift,apple/swift,JGiola/swift,glessard/swift,benlangmuir/swift,roambotics/swift,JGiola/swift,benlangmuir/swift,glessard/swift,glessard/swift,benlangmuir/swift,JGiola/swift,apple/swift,benlangmuir/swift,apple/swift,roambotics/swift