Remove nonprinting characters when escaping JSON.

Change-Id: I41fe97db4cee333e601356253f28186ef4036237

examples/inspect.c

@@ -258,7 +258,9 @@ int put_str_with_escape(char *buffer, const char *str) {
   int i;
   int j = 0;
   for (i = 0; str[i] != '\0'; i++) {
-    if (str[i] == '"' || str[i] == '\\') {
+    if (str[i] < ' ') {
+      continue;
+    } else if (str[i] == '"' || str[i] == '\\') {
       buffer[j++] = '\\';
     }
     buffer[j++] = str[i];