Move the definitions of EC_KEY and EC_KEY_METHOD to ossl_typ.h

Most of all, that has inclusion of openssl/engine.h work even if EC
has been disabled.  This is the same as has been done for DH, DSA, RSA
and more...

Reviewed-by: Stephen Henson <steve@openssl.org>

include/openssl/ec.h

diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index 9f0a009..a7793b8 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -740,9 +740,6 @@
 /*                      EC_KEY functions                            */
 /********************************************************************/
 
-typedef struct ec_key_st EC_KEY;
-typedef struct ec_key_method_st EC_KEY_METHOD;
-
 /* some values for the encoding_flag */
 # define EC_PKEY_NO_PARAMETERS   0x001
 # define EC_PKEY_NO_PUBKEY       0x002

include/openssl/ossl_typ.h

diff --git a/include/openssl/ossl_typ.h b/include/openssl/ossl_typ.h
index 167974b..a6d07a0 100644
--- a/include/openssl/ossl_typ.h
+++ b/include/openssl/ossl_typ.h
@@ -148,6 +148,9 @@
 typedef struct rsa_st RSA;
 typedef struct rsa_meth_st RSA_METHOD;
 
+typedef struct ec_key_st EC_KEY;
+typedef struct ec_key_method_st EC_KEY_METHOD;
+
 typedef struct rand_meth_st RAND_METHOD;
 
 typedef struct x509_st X509;