RCPT TO wrong format

Hi!

In case that one tries to send a mail from an email address of the form Name <mail@domain.com>, cl-smtp does not work with certain SMTP servers, such as Google SMTP. This is because the address (w/ the name) is sent verbatim in the RCPT TO command (e.g. RCPT TO: <Name <mail@domain.com>>), which causes the SMTP server to throw an error, complaining about invalid syntax. I fixed this by stripping the name part from the address in the RCPT TO command in case that it is present.

Since I can't open a pull request here, I'm attaching the patch herecl-smtp.patch. It makes an assumption about the email address not being malformed.

Cheers!