update ecdsa doc

 ECDSA_SIG*	d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, 

		long len);

 ECDSA_DATA*	ECDSA_DATA_new(void);

 ECDSA_DATA*	ECDSA_DATA_new_method(ENGINE *eng);

 void		ECDSA_DATA_free(ECDSA_DATA *data);

 ECDSA_DATA*	ecdsa_check(EC_KEY *eckey);

 ECDSA_SIG*	ECDSA_do_sign(const unsigned char *dgst, int dgst_len,

			EC_KEY *eckey);

 ECDSA_SIG*	ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, 

			const BIGNUM *kinv, const BIGNUM *rp,

			EC_KEY *eckey);

 int		ECDSA_do_verify(const unsigned char *dgst, int dgst_len,

			const ECDSA_SIG *sig, EC_KEY* eckey);

 int		ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,

 int		ECDSA_sign(int type, const unsigned char *dgst,

			int dgstlen, unsigned char *sig,

			unsigned int *siglen, EC_KEY *eckey);

 int		ECDSA_sign_ex(int type, const unsigned char *dgst,

			int dgstlen, unsigned char *sig,

			unsigned int *siglen, const BIGNUM *kinv, 

			const BIGNUM *rp, EC_KEY *eckey);

 int		ECDSA_verify(int type, const unsigned char *dgst,

			int dgstlen, const unsigned char *sig,

			int siglen, EC_KEY *eckey);

B<*sig> points to the buffer containing the DER encoded signature

of size B<len>.

The B<ECDSA_DATA> structure extends the B<EC_KEY_METH_DATA>

structure with ECDSA specific data.

 struct

	{

	/* EC_KEY_METH_DATA part */

	int  (*init)(EC_KEY *);

	void (*finish)(EC_KEY *);

	/* method (ECDSA) specific part */

	BIGNUM	*kinv;	/* signing pre-calc */

	BIGNUM	*r;	/* signing pre-calc */

	...

	} 

 ECDSA_DATA;

B<kinv> and B<r> are used to store precomputed values (see

B<ECDSA_sign_setup>). 

ECDSA_DATA_new() returns a newly allocated and initialized

B<ECDSA_DATA> structure (or NULL on error). 

ECDSA_DATA_free() frees the B<ECDSA_DATA> structure B<data>.

ecdsa_check() returns the pointer to the B<ECDSA_DATA>

structure in B<EC_KEY-E<gt>meth_data> (if B<EC_KEY-E<gt>meth_data>

is not a pointer to a B<ECDSA_DATA> structure then the old

data is freed and a new B<ECDSA_DATA> structure is allocated

using B<ECDSA_DATA_new>).

ECDSA_size() returns the maximum length of a DER encoded

ECDSA signature created with the private EC key B<eckey>.

signing operation. B<eckey> is the private EC key and B<ctx>

is a pointer to B<BN_CTX> structure (or NULL). The precomputed

values or returned in B<kinv> and B<rp> and can be used in a

later call to B<ECDSA_sign> or B<ECDSA_do_sign> when placed in

B<ECDSA_DATA-E<gt>kinv> and B<ECDSA_DATA-E<gt>r>.

later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>.

ECDSA_sign() is wrapper function for ECDSA_sign_ex with B<kinv>

and B<rp> set to NULL.

ECDSA_sign() computes a digital signature of the B<dgstlen> bytes

hash value B<dgst> using the private EC key B<eckey> and places

the DER encoding of the created signature in B<sig>. The length

of the created signature is returned in B<sig_len>. Note: B<sig>

ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes

hash value B<dgst> using the private EC key B<eckey> and the optional

pre-computed values B<kinv> and B<rp>. The DER encoded signatures is

stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig>

must point to B<ECDSA_size> bytes of memory. The parameter B<type>

is ignored.

value B<dgst> of size B<dgstlen> using the public key B<eckey>.

The parameter B<type> is ignored.

ECDSA_do_sign() computes a digital signature of the B<dgst_len>

bytes hash value B<dgst> using the private key B<eckey> and 

returns the signature in a newly allocated B<ECDSA_SIG> structure

(or NULL on error).

ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv>

and B<rp> set to NULL.

ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len>

bytes hash value B<dgst> using the private key B<eckey> and the

optional pre-computed values B<kinv> and B<rp>. The signature is

returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error).

ECDSA_do_verify() verifies that the signature B<sig> is a valid

ECDSA signature of the hash value B<dgst> of size B<dgst_len>