The options which emulate a web server don't make sense when doing DTLS.
Exit with an error if an attempt is made to use them.

PR#3453
(cherry picked from commit 58a2aaeade8bdecd0f9f0df41927f7cff3012547)

PR#3445
(cherry picked from commit 1c3e9a7c)

Add description of the option to advertise support of
Next Protocol Negotiation extension (-nextprotoneg) to
man pages of s_client and s_server.

PR#3444
(cherry picked from commit 7efd0e77)

(cherry picked from commit 7aabd9c92fe6f0ea2a82869e5171dcc4518cee85)

This is actually ok for this function, but initialised to zero anyway if
PURIFY defined.

This does have the impact of masking any *real* unitialised data reads in bn though.

Patch based on approach suggested by Rich Salz.

PR#3415

(cherry picked from commit 77747e2d9a5573b1dbc15e247ce18c03374c760c)

PR#3440
(cherry picked from commit 924e5eda)

  Detected by dcruette@qualitesys.com

(cherry picked from commit 8b5dd340)

(cherry picked from commit c1d1b011)

Based on an original patch by Neitrino Photonov <neitrinoph@gmail.com>

PR#3439

(cherry picked from commit 66816c53)

(cherry picked from commit 1b0fe79f)

(cherry picked from commit d11c70b2)

PR: #3424,#3423,#3422
(cherry picked from commit 021e5043)

(cherry picked from commit c4f8efab)

(cherry picked from commit 07b635cc)

PR#2985
(cherry picked from commit 9d23f422)

Based on feedback from Jeffrey Walton.

(cherry picked from commit b73ac027)

Reduces number of silly casts in OpenSSL code and likely most
applications.  Consistent with (char *) for "peername" value from
X509_check_host() and X509_VERIFY_PARAM_get0_peername().

(cherry picked from commit 297c67fc)

Pass address of X509_VERIFY_PARAM_ID peername to X509_check_host().
Document modified interface.

(cherry picked from commit ced3d915)

Declaration, memory management, accessor and documentation.

(cherry picked from commit 6e661d45)

(cherry picked from commit eef1827f)

(cherry picked from commit 90b70a6a)

Implemented as STACK_OF(OPENSSL_STRING).

(cherry picked from commit 8abffa4a)

(cherry picked from commit 66d884f0)

(cherry picked from commit ee724df7)

(cherry picked from commit cba3f1c7)

(cherry picked from commit a44f219c)

(cherry picked from commit a23a6e85)

PR#2277
(cherry picked from commit 733a6c882e92f8221bd03a51643bb47f5f81bb81)

(cherry picked from commit 07255f0a76d9d349d915e14f969b9ff2ee0d1953)

PR: #3431
(cherry picked from commit 7eb9680a)

(cherry picked from commit 0e7a32b5)

(cherry picked from commit 375a64e3)

PR#3418.
(cherry picked from commit fdea4fff)

PR#319 (reoponed version).
(cherry picked from commit 7f6e9578)

(cherry picked from commit 55707a36)

Remove RFC5878 code. It is no longer needed for CT and has numerous bugs.

(cherry picked from commit f1112985)