message: Fix variable shadowing in pubkey.cpp
  pubkey.cpp:324:55: warning: declaration shadows a field of 'CExtPubKey' [-Wshadow]
  bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const
  ^
  ./pubkey.h:169:18: note: previous declaration is here
  unsigned int nChild;
  ^
diff: @@ -275,13 +275,13 @@ bool CPubKey::Decompress()
  return true;
  }
  -bool CPubKey::Derive(CPubKey &pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode &cc) const
  +bool CPubKey::Derive(CPubKey &pubkeyChild, ChainCode &ccChild, unsigned int _nChild, const ChainCode &cc) const
  {
  assert(IsValid());
  - assert((nChild >> 31) == 0);
  + assert((_nChild >> 31) == 0);
  assert(begin() + 33 == end());
  unsigned char out[64];
  - BIP32Hash(cc, nChild, *begin(), begin() + 1, out);
  + BIP32Hash(cc, _nChild, *begin(), begin() + 1, out);
  memcpy(ccChild.begin(), out + 32, 32);
  secp256k1_pubkey pubkey;
  if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size()))
  @@ -321,13 +321,13 @@ void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE])
  pubkey.Set(code + 41, code + BIP32_EXTKEY_SIZE);
  }
  -bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const
  +bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const
  {
  out.nDepth = nDepth + 1;
  CKeyID id = pubkey.GetID();
  memcpy(&out.vchFingerprint[0], &id, 4);
  - out.nChild = nChild;
  - return pubkey.Derive(out.pubkey, out.chaincode, nChild, chaincode);
  + out.nChild = _nChild;
  + return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
  }
  /* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char> &vchSig)
  