refactor: Avoid &foo[0] on C-Style arrays

This is confusing at best when parts of a class use the
redundant operators and other parts do not.

src/pubkey.cpp

@@ -293,7 +293,7 @@ void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
 bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
     out.nDepth = nDepth + 1;
     CKeyID id = pubkey.GetID();
-    memcpy(&out.vchFingerprint[0], &id, 4);
+    memcpy(out.vchFingerprint, &id, 4);
     out.nChild = _nChild;
     return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
 }