Test split, coalesced-split and empty handshake records

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index f1fe0ec..dba8d74 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -3699,6 +3699,7 @@
     rec->buf_len = rec->data_offset + rec->data_len;
 
     if (rec->data_len == 0) {
+        MBEDTLS_SSL_DEBUG_MSG(1, ("rejecting empty record"));
         return MBEDTLS_ERR_SSL_INVALID_RECORD;
     }