check length properly

Submitted by: Peter Sylvester
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index d755886..69c0d42 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -221,7 +221,7 @@
 		/* Add TLS extension EllipticCurves to the ClientHello message */
 		long lenmax; 
 
-		if ((lenmax = limit - p - 5) < 0) return NULL; 
+		if ((lenmax = limit - p - 6) < 0) return NULL; 
 		if (s->tlsext_ellipticcurvelist_length > (unsigned long)lenmax) return NULL;
 		if (s->tlsext_ellipticcurvelist_length > 255)
 			{