Use named curve parameter encoding by default.

Many applications require named curve parameter encoding instead of explicit
parameter encoding (including the TLS library in OpenSSL itself). Set this
encoding by default instead of requiring an explicit call to set it.

Add OPENSSL_EC_EXPLICT_CURVE define.
Reviewed-by: NMatt Caswell <matt@openssl.org>

crypto/ec/ec.h

@@ -715,7 +715,8 @@ int EC_GROUP_get_pentanomial_basis(const EC_GROUP *, unsigned int *k1,
                                    unsigned int *k2, unsigned int *k3);
 # endif
 
-# define OPENSSL_EC_NAMED_CURVE  0x001
+# define OPENSSL_EC_EXPLICIT_CURVE  0x000
+# define OPENSSL_EC_NAMED_CURVE     0x001
 
 typedef struct ecpk_parameters_st ECPKPARAMETERS;
 

crypto/ec/ec_lib.c

@@ -106,7 +106,7 @@ EC_GROUP *EC_GROUP_new(const EC_METHOD *meth)
         goto err;
 
     ret->curve_name = 0;
-    ret->asn1_flag = 0;
+    ret->asn1_flag = OPENSSL_EC_NAMED_CURVE;
     ret->asn1_form = POINT_CONVERSION_UNCOMPRESSED;
 
     ret->seed = NULL;