Fixed FormatSummaryItems() to follow rfc3501 more strictly
Fixed FormatSummaryItems() to follow rfc3501 more strictly

nachocove/MailKit,rajeshwarn/MailKit,jamie-dainton/MailKit,dsbenghe/MailKit,mganss/MailKit,FubarDevelopment/MailKit,sstraus/MailKit,jstedfast/MailKit,matt2003/MailKit,eino-makitalo/MailKit