Change to use inline function instead of macro.
Change to use inline function instead of macro.

This makes FauxPas's localization checks work properly.

NewAmsterdamLabs/stripe-ios,stripe/stripe-ios,fbernardo/stripe-ios,stripe/stripe-ios,NewAmsterdamLabs/stripe-ios,NewAmsterdamLabs/stripe-ios,fbernardo/stripe-ios,stripe/stripe-ios,fbernardo/stripe-ios,stripe/stripe-ios,NewAmsterdamLabs/stripe-ios,fbernardo/stripe-ios,stripe/stripe-ios,stripe/stripe-ios