GMail IMAP secretly supports LITERAL+ except for APPEND
GMail IMAP secretly supports LITERAL+ except for APPEND

This patch optimizes commands such as SEARCH that can
benefit from the use of LITERAL+ for generally smallish
strings.

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