Const-correct ASN1_OBJECT_create.

The implementation is a little goofy, but OBJ_dup internally makes a
copy of all the data.

Change-Id: I58e6804ede00100211ac112f03e26a34a2d29b5a
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/47125
Reviewed-by: Adam Langley <agl@google.com>

crypto/asn1/a_object.c

@@ -263,7 +263,7 @@ void ASN1_OBJECT_free(ASN1_OBJECT *a)
         OPENSSL_free(a);
 }
 
-ASN1_OBJECT *ASN1_OBJECT_create(int nid, unsigned char *data, int len,
+ASN1_OBJECT *ASN1_OBJECT_create(int nid, const unsigned char *data, int len,
                                 const char *sn, const char *ln)
 {
     ASN1_OBJECT o;

include/openssl/asn1.h

@@ -883,7 +883,8 @@ OPENSSL_EXPORT int i2a_ASN1_STRING(BIO *bp, const ASN1_STRING *a, int type);
 OPENSSL_EXPORT int i2t_ASN1_OBJECT(char *buf, int buf_len,
                                    const ASN1_OBJECT *a);
 
-OPENSSL_EXPORT ASN1_OBJECT *ASN1_OBJECT_create(int nid, unsigned char *data,
+OPENSSL_EXPORT ASN1_OBJECT *ASN1_OBJECT_create(int nid,
+                                               const unsigned char *data,
                                                int len, const char *sn,
                                                const char *ln);