further picotcp api coverage

ext/picotcp/stack/pico_protocol.c

@@ -11,6 +11,13 @@
 #include "pico_protocol.h"
 #include "pico_tree.h"
 
+/*
+static pico_err_t get_pico_err()
+{
+    return pico_err;
+}
+*/
+
 struct pico_proto_rr
 {
     struct pico_tree *t;