Make {d2i,i2d}_PrivateKey() fall back to PKCS#8 format if no legacy format
supported. Add support in d2i_AutoPrivateKey().

- hide the EC_KEY structure definition in ec_lcl.c + add
  some functions to use/access the EC_KEY fields
- change the way how method specific data (ecdsa/ecdh) is
  attached to a EC_KEY
- add ECDSA_sign_ex and ECDSA_do_sign_ex functions with
  additional parameters for pre-computed values
- rebuild libeay.num from 0.9.7

Submitted by: Nils Larsch

Submitted by: Nils Larsch <nla@trustcenter.de>

sure they are available in opensslconf.h, by giving them names starting
with "OPENSSL_" to avoid conflicts with other packages and by making
sure e_os2.h will cover all platform-specific cases together with
opensslconf.h.

I've checked fairly well that nothing breaks with this (apart from
external software that will adapt if they have used something like
NO_KRB5), but I can't guarantee it completely, so a review of this
change would be a good thing.

Submitted by:
Reviewed by:
PR: