Get rid of ubjson

PUBLISHED_FROM=e6f1dca95ec7ed3795adf493cca9cdcdc07381f5

mongoose.c

@@ -971,6 +971,11 @@ struct mg_str mg_mk_str(const char *s) {
   return ret;
 }
 
+struct mg_str mg_mk_str_n(const char *s, size_t len) {
+  struct mg_str ret = {s, len};
+  return ret;
+}
+
 int mg_vcmp(const struct mg_str *str1, const char *str2) {
   size_t n2 = strlen(str2), n1 = str1->len;
   int r = memcmp(str1->p, str2, (n1 < n2) ? n1 : n2);