Add test that A+A = 2×A on elliptic curves.

Change-Id: I914efab9a15c903f79a1b83388b577b14c534269
Reviewed-on: https://boringssl-review.googlesource.com/7247
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index 55ba194..5aff728 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -194,8 +194,8 @@
 OPENSSL_EXPORT int EC_POINT_is_on_curve(const EC_GROUP *group,
                                         const EC_POINT *point, BN_CTX *ctx);
 
-/* EC_POINT_cmp returns zero if |a| is equal to |b|, greater than zero is
- * non-equal and -1 on error. If |ctx| is not NULL, it may be used. */
+/* EC_POINT_cmp returns zero if |a| is equal to |b|, greater than zero if
+ * not equal and -1 on error. If |ctx| is not NULL, it may be used. */
 OPENSSL_EXPORT int EC_POINT_cmp(const EC_GROUP *group, const EC_POINT *a,
                                 const EC_POINT *b, BN_CTX *ctx);