imap-send: move #ifdef around

Instead of adding an early return to the inside of the
ssl_socket_connect() function for NO_OPENSSL compilation, split it
into a separate stub function.

No functional change, but the next change to extend ssl_socket_connect()
will become easier to read this way.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
imap-send: the subject of SSL certificate must match the host

We did not check a valid certificate's subject at all, and would
have happily talked with a wrong host after connecting to an
incorrect address and getting a valid certificate that does not
belong to the host we intended to talk to.

Signed-off-by: Oswald Buddenhagen <ossi@kde.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
imap-send: support subjectAltName as well

Check not only the common name of the certificate subject, but also
check the subject alternative DNS names as well, when verifying that
the certificate matches that of the host we are trying to talk to.

Signed-off-by: Oswald Buddenhagen <ossi@kde.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'ob/imap-send-ssl-verify' into maint

* ob/imap-send-ssl-verify:
  imap-send: support subjectAltName as well
  imap-send: the subject of SSL certificate must match the host
  imap-send: move #ifdef around
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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