Fix eckey_priv_encode()

Fix eckey_priv_encode to return an error on failure of i2d_ECPrivateKey.
Fix version documentation.

Specify -f is for compilation flags. Add -d to synopsis section.

(cherry picked from commit 006397ea62bbcae22c8664d53c2222b808c4bdd1)

Closes #80.
Merge pull request #1 from openssl/OpenSSL_1_0_0-stable

Open ssl 1 0 0 stable