fix EC_GROUP_copy for EC_GFp_nist_method()

Submitted by: Nils Larsch
diff --git a/crypto/ec/ec_lcl.h b/crypto/ec/ec_lcl.h
index 06e6669..f4e9700 100644
--- a/crypto/ec/ec_lcl.h
+++ b/crypto/ec/ec_lcl.h
@@ -322,6 +322,7 @@
 
 
 /* method functions in ecp_nist.c */
+int ec_GFp_nist_group_copy(EC_GROUP *dest, const EC_GROUP *src);
 int ec_GFp_nist_group_set_curve(EC_GROUP *, const BIGNUM *p, const BIGNUM *a, const BIGNUM *b, BN_CTX *);
 int ec_GFp_nist_field_mul(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *);
 int ec_GFp_nist_field_sqr(const EC_GROUP *, BIGNUM *r, const BIGNUM *a, BN_CTX *);