Sync DH error codes with HEAD.

misleading/obsolete comment [from HEAD].

Also use FIPS EC methods unconditionally for now: might want to use them
only in FIPS mode or with a switch later.

Move compression, point2oct and oct2point functions into separate files.

Add a flags field to EC_METHOD.

Add a flag EC_FLAGS_DEFAULT_OCT to use the default compession and oct functions
(all existing methods do this). This removes dependencies from EC_METHOD while
keeping original functionality.

Backport from HEAD with minor changes.

New option to disable characteristic two fields in EC code.

Make no-ec2m work on Win32 build.

use of assembly language routines: rename the assembly language function
to the private_* variant unconditionally and perform tests from a small
C wrapper.

of assuming they will always suceed.

New function X509_ALGOR_set_md() to set X509_ALGOR (DigestAlgorithmIdentifier) from a digest algorithm (backport from HEAD).

Digest sign, verify operations are not redirected at this stage.

This is needed to handle FIPS redirection fully.

Not complete: ciphers with assembly language key setup are not
covered yet.

digest in use: this caused the PRF to fail for an odd premaster secret
length.