Add new methods DTLS_*_method() which support both DTLS 1.0 and DTLS 1.2 and
pick the highest version the peer supports during negotiation.

As with SSL/TLS options can change this behaviour specifically
SSL_OP_NO_DTLSv1 and SSL_OP_NO_DTLSv1_2.

Don't use Win32 specific options in mk1mf.pl to build assembly language
files.

turn out to be made somewhere by existing Makefiles.

Only use -MMD and .sinclude in copy builds: other platforms don't
support them.

Since s->method does not reflect the final client version when a client
hello is sent for SSLv23_client_method it can't be relied on to indicate
if TLS 1.2 ciphers should be used. So use the client version instead.

Give CBC decrypt approximately same treatment as to CTR and collect 25%.

Submitted by: David Miller

(cherry picked from commit 944bc29f)

Port TLS 1.2 GCM code to DTLS. Enable use of TLS 1.2 only ciphers when in
DTLS 1.2 mode too.

The relaxed signing requirements for fixed DH certificates apply to DTLS 1.2
too.

Add DTLS1.2 support for cached records when computing handshake macs
instead of the MD5+SHA1 case for DTLS < 1.2 (this is a port of the
equivalent TLS 1.2 code to DTLS).