VideoSubscriberAccount macOS 10.14 to 10.15 API Differences

VideoSubscriberAccountDefines.h
Added #def VS_INTERNAL_EXPORT
Added #def VS_INTERNAL_EXTERN
VideoSubscriberAccountErrors.h
Added VSErrorCodeRejected
VSAccountMetadataRequest.h
Added VSAccountMetadataRequest.accountProviderAuthenticationToken
VSAccountProviderResponse.h
Added VSAccountProviderAuthenticationSchemeAPI