v15 hardfork testing
I've set up a testnet p2pool to check that everything works correctly during the v15 hardfork. Testnet will fork to v15 at block 1982800 (around 08:00 UTC on May 16th).

How to join the test:

- Compile the latest Monero binaries from the source (follow the [compilation instructions](https://github.com/monero-project/monero#compiling-monero-from-source))
- Compile the latest P2Pool binaries from the source
- Run Monero and wait until it fully syncs the testnet:
```
./monerod --testnet --zmq-pub tcp://127.0.0.1:28083 --disable-dns-checkpoints --enable-dns-blocklist
```
- Create a new testnet wallet
- Run P2Pool:
```
./p2pool --wallet YOUR_TESTNET_WALLET --stratum 0.0.0.0:8888 --p2p 0.0.0.0:37887 --rpc-port 28081 --zmq-port 28083 --addpeers p2pool.io:37887
```
- If you did everything right, you should see `Side chain ID = 6126482d************************************************1ba7c94b` in p2pool status
- Start mining either by running `start_mining 1` in p2pool console, or by running `./xmrig -o 127.0.0.1:8888 -t 1` (1 mining thread will be enough for testing, we don't need a lot of hashrate in this test)