SegwitAddress: Don't encode witness version to OP_N when constructing.

This bug was never exposed outside the SegwitAddress class (and thus can't be tested) because the encode method is only ever called by fromHash, where the script version is always set to 0.

Nevertheless, this bug could result in faults in future code, as other witness program versions begin to be used: The other construction methods, such as fromBech32(), leave the version byte as a simple representation of the version number. This means that, were the SegwitAddress constructor ever called with a non-0 version number, getWitnessVersion() would return an incorrect result, and ScriptBuilder.createOutputScript() would fail, re-running encodeToOpN() on the now greater-than-16 version byte.

core/src/main/java/org/bitcoinj/core/SegwitAddress.java

@@ -71,7 +71,7 @@ public class SegwitAddress extends Address {
     private static byte[] encode(int witnessVersion, byte[] witnessProgram) throws AddressFormatException {
         byte[] convertedProgram = convertBits(witnessProgram, 0, witnessProgram.length, 8, 5, true);
         byte[] bytes = new byte[1 + convertedProgram.length];
-        bytes[0] = (byte) (Script.encodeToOpN(witnessVersion) & 0xff);
+        bytes[0] = (byte) (witnessVersion & 0xff);
         System.arraycopy(convertedProgram, 0, bytes, 1, convertedProgram.length);
         return bytes;
     }