Create ecp_group_copy() and use it
diff --git a/library/ecp.c b/library/ecp.c
index a2d13c4..09a021b 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -182,6 +182,14 @@
 }
 
 /*
+ * Copy the contents of a group object
+ */
+int ecp_group_copy( ecp_group *dst, const ecp_group *src )
+{
+    return ecp_use_known_dp( dst, src->id );
+}
+
+/*
  * Import a non-zero point from ASCII strings
  */
 int ecp_point_read_string( ecp_point *P, int radix,