Implement native UDP transport reliability (#52)

tests/compat/tests/core_runtime_shims.rs

@@ -106,8 +106,8 @@ fn client_and_settings_construct_without_starting_runtime_work() {
         member_id(CapsRateLimiter::new_with_constructor()),
         "M:LibreMetaverse.CapsRateLimiter.#ctor"
     );
-    assert_eq!(
-        member_id(UDPPacketBuffer::new_with_constructor()),
-        "M:LibreMetaverse.UDPPacketBuffer.#ctor"
-    );
+    let udp_buffer = UDPPacketBuffer::new_with_constructor().expect("UDP packet buffer");
+    assert_eq!(udp_buffer.data.len(), 4096);
+    assert_eq!(udp_buffer.data_length, 0);
+    assert_eq!(udp_buffer.remote_end_point, "0.0.0.0:0".parse().unwrap());
 }