changed 
` int mailimap_is__complex_command_tag_enabled(mailimap * imap); `
` void mailimap_set_complex_command_tag_enabled(mailimap * imap, int enabled);`
to
`int mailimap_is_163_workaround_enabled(mailimap * imap);`
`void mailimap_set_163_workaround_enabled(mailimap * imap, int enabled);`

163 mail server will reject the command which with a number tag.

Implements two functions:
mailimap_oauth2_authenticate: Use to to send the authentication token
to the server and actually authenticate with it.
mailimap_oauth2_authenticate_send Builds and sends the authentication
string in the form of base64("user=" {User} "^Aauth=Bearer " {Access
Token} "^A^A")`
This has been tested against Gmail.

http://tools.ietf.org/html/rfc5256