Added the ability to use an XOAUTH2 bearer token [RFC6750] with POP3 for
authentication using RFC6749 "OAuth 2.0 Authorization Framework".

The bearer token is expected to be valid for the user specified in
conn->user. If CURLOPT_XOAUTH2_BEARER is defined and the connection has
an advertised auth mechanism of "XOAUTH2", the user and access token are
formatted as a base64 encoded string and sent to the server as
"AUTH XOAUTH2 <bearer token>".

... that these options apply to SMTP only.

iOS 7 finally added the option to enable 1/n-1 when using TLS 1.0
and a CBC cipher, so we now always turn that on unless the user
manually turns it off using CURLSSLOPT_ALLOW_BEAST.

It appears Apple also added some new PSK ciphers, but no interface to
use them yet, so we at least support printing them if we find them.

...rather than specify a customised EHLO response.

...to not be as strict as it was rejecting valid numeric email
addresses.

Possible unintended interpolation in string at line 796

Following changes to ftpserver.pl fixed the mail from address to be a
correctly formatted address otherwise the server response will be 501
Invalid address.

Can't modify constant item in scalar assignment line 779, near "0;"

MAIl_smtp() will now check for a correctly formatted FROM address as
well as the optional SIZE parameter comparing it against the server
capability when specified.

Implement: Expired Cookies These following situation, curl removes
cookie(s) from struct CookieInfo if the cookie expired.
 - Curl_cookie_add()
 - Curl_cookie_getlist()
 - cookie_output()

Avoid 'interface' literal that some MinGW versions define as a macro

Additionally, corrected some very, very minor coding style errors.

By default the mail server doesn't send the SIZE capability but instead
it has to be specified as a supported capability.

For example:

CAPA "SIZE 1048576" 8BITMIME BINARYMIME

will populate the capabilities list with the following in:

SIZE 1048576
8BITMIME
BINARYMIME

Can't modify constant item in postincrement line 727, near "i++"

...and updated test902 as explicit HELO response is no longer required.

...in both the IMAP LOGIN and POP3 PASS handlers introduced in commit
187ac693 and 84ad1569 respectively.

...which was accidentally introduced in commit 4d6ef629.