* repeater: onAnonDataRecv(), now rejecting non-ASCII password (preparing for future request codes)

* repeater: DISCOVER requests now with a simple RateLimiter (max 4, every 2 minutes)

examples/simple_repeater/RateLimiter.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <stdint.h>
+
+class RateLimiter {
+  uint32_t _start_timestamp;
+  uint32_t _secs;
+  uint16_t _maximum, _count;
+
+public:
+  RateLimiter(uint16_t maximum, uint32_t secs): _maximum(maximum), _secs(secs), _start_timestamp(0), _count(0) { }
+
+  bool allow(uint32_t now) {
+    if (now < _start_timestamp + _secs) {
+      _count++;
+      if (_count > _maximum) return false;   // deny
+    } else {   // time window now expired
+      _start_timestamp = now;
+      _count = 1;
+    }
+    return true;
+  }
+};