Adding conformance to AdditiveArithmetic to fix compilation error in Swift5
Adding conformance to AdditiveArithmetic to fix compilation error in Swift5

Signed-off-by: Cédric Foellmi <240633aa59d25638de9800ef43a88ad2e208d24d@onekiloparsec.dev>

onekiloparsec/SwiftAA,alex-vasenin/SwiftAA,alex-vasenin/SwiftAA,onekiloparsec/SwiftAA,alex-vasenin/SwiftAA,onekiloparsec/SwiftAA,onekiloparsec/SwiftAA,alex-vasenin/SwiftAA,alex-vasenin/SwiftAA,onekiloparsec/SwiftAA