New test function inject_client_content_on_the_wire()

Not used for real stuff so far, just getting the tooling in place.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 693edc7..fdf8634 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1380,6 +1380,7 @@
     }
 
     if (ret == 0) {
+        MBEDTLS_SSL_DEBUG_MSG(2, ("no supported_versions extension"));
         return SSL_CLIENT_HELLO_TLS1_2;
     }
 
@@ -1401,6 +1402,7 @@
          * the TLS version to negotiate.
          */
         if (MBEDTLS_SSL_VERSION_TLS1_2 == ret) {
+            MBEDTLS_SSL_DEBUG_MSG(2, ("supported_versions without 1.3"));
             return SSL_CLIENT_HELLO_TLS1_2;
         }
     }
@@ -1985,6 +1987,7 @@
         }
         ssl->keep_current_message = 1;
         ssl->tls_version = MBEDTLS_SSL_VERSION_TLS1_2;
+        MBEDTLS_SSL_DEBUG_MSG(1, ("non-1.3 ClientHello left for later processing"));
         return 0;
     }