Refactor: Require scriptPubKey to get wallet SigningProvider

Easier to review ignoring whitespace:

    git log -p -n1 -w

This commit does not change behavior. It passes new CScript arguments to
signing functions, but the arguments aren't currently used.

src/qt/coincontroldialog.cpp

@@ -468,7 +468,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
         {
             CPubKey pubkey;
             PKHash *pkhash = boost::get<PKHash>(&address);
-            if (pkhash && model->wallet().getPubKey(CKeyID(*pkhash), pubkey))
+            if (pkhash && model->wallet().getPubKey(out.txout.scriptPubKey, CKeyID(*pkhash), pubkey))
             {
                 nBytesInputs += (pubkey.IsCompressed() ? 148 : 180);
             }

src/qt/signverifymessagedialog.cpp

@@ -136,7 +136,7 @@ void SignVerifyMessageDialog::on_signMessageButton_SM_clicked()
     }
 
     CKey key;
-    if (!model->wallet().getPrivKey(CKeyID(*pkhash), key))
+    if (!model->wallet().getPrivKey(GetScriptForDestination(destination), CKeyID(*pkhash), key))
     {
         ui->statusLabel_SM->setStyleSheet("QLabel { color: red; }");
         ui->statusLabel_SM->setText(tr("Private key for the entered address is not available."));