Merge pull request #557 from h2o/kazuho/missing-includes-freebsd

add includes (otherwise fails to compile on freebsd)
diff --git a/lib/picotls.c b/lib/picotls.c
index 9945535..00261a5 100644
--- a/lib/picotls.c
+++ b/lib/picotls.c
@@ -2386,7 +2386,7 @@
                 }
             }
             assert(tls->cipher_suite != NULL && "no compatible cipher-suite provided that matches psk.hash");
-            if (properties->client.max_early_data_size != NULL) {
+            if (properties != NULL && properties->client.max_early_data_size != NULL) {
                 tls->client.using_early_data = 1;
                 *properties->client.max_early_data_size = SIZE_MAX;
             }