It would be nice if there was a way to tell compilers not to drop the lock stack and thus issue warnings when accessing a symbol that needs a lock inside `Assume`/`Assert`.

Hit by (at least): @ajtowns , @jnewbery , me.
"1KqbBpLy5FARmTPD4VZnDDpYjkUvkr82Pm",
            "invalid signature, not in base64 encoding",
            "message should be irrelevant"),
        MessageVerificationResult::ERR_MALFORMED_SIGNATURE);
    BOOST_CHECK_EQUAL(
        MessageVerify(
            "1KqbBpLy5FARmTPD4VZnDDpYjkUvkr82Pm",
            "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
            "message should be irrelevant"),
        MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED);
    BOOST_CHECK_EQUAL(
        MessageVerify(
            "15CRxFdyRpGZLW9w8HnHvVduizdL5jKNbs",
            "IPojfrX2dfPnH26UegfbGQQLrdK844DlHq5157/P6h57WyuS/Qsl+h/WSVGDF4MUi4rWSswW38oimDYfNNUBUOk=",
            "I never signed this"),
        MessageVerificationResult::ERR_NOT_SIGNED);
    BOOST_CHECK_EQUAL(
        MessageVerify(
            "15CRxFdyRpGZLW9w8HnHvVduizdL5jKNbs",
            "IPojfrX2dfPnH26UegfbGQQLrdK844DlHq5157/P6h57WyuS/Qsl+h/WSVGDF4MUi4rWSswW38oimDYfNNUBUOk=",
            "Trust no one"),
        MessageVerificationResult::OK);
    BOOST_CHECK_EQUAL(
        MessageVerify(
            "11canuhp9X2NocwCq7xNrQYTmUgZAnLK3",
            "IIcaIENoYW5jZWxsb3Igb24gYnJpbmsgb2Ygc2Vjb25kIGJhaWxvdXQgZm9yIGJhbmtzIAaHRtbCeDZINyavx14=",
            "Trust me"),
        MessageVerificationResult::OK);
}
BOOST_AUTO_TEST_CASE(message_hash)