Good afternoon,

In the attached 4 commits I have implemented OAUTH 2.0[1] Bearer
Token[2] support to SMTP and IMAP.

This implementation allows for authentication to an SMTP or IMAP
server using only the username and an OAUTH 2.0[1] Bearer token[2].

The construction of the token format matches the GMAIL
xoauth2_protocol[3] format specifically, and may need to be broadened
to support other implementations; I do not presently have access to
other providers for testing.

None of the included changes make any attempt to implement OAUTH 2.0
for HTTP/HTTPS requests, as that is presently outside the scope of my
immediate needs.

Hopefully this is useful and versatile enough for inclusion into cURL
with minimal reworking.

I look forward to hearing about any suggested alterations/improvements.

references -
[1] http://tools.ietf.org/html/rfc6749
[2] http://tools.ietf.org/html/rfc6750
[3] https://developers.google.com/gmail/xoauth2_protocol

-- 
Kyle L. Huff
http://curetheitch.com/
http://webpg.org/

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