Function EOS_Auth_GetMergedAccountsCount 

pub unsafe extern "C" fn EOS_Auth_GetMergedAccountsCount(
    Handle: EOS_HAuth,
    LocalUserId: EOS_EpicAccountId,
) -> u32

Fetch the number of merged accounts for a given logged in account.

@param LocalUserId The account ID of a currently logged in account.

@return the number of merged accounts for the logged in account.