signals: use forwarding header for boost signals

For now, including btcsignals.h simply includes boost's signals. A follow-up
commit will replace the implementation.

src/btcsignals.h

@@ -0,0 +1,12 @@
+// Copyright (c) The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_BTCSIGNALS_H
+#define BITCOIN_BTCSIGNALS_H
+
+#include <boost/signals2/connection.hpp>
+#include <boost/signals2/optional_last_value.hpp>
+#include <boost/signals2/signal.hpp>
+
+#endif // BITCOIN_BTCSIGNALS_H

src/common/interfaces.cpp

@@ -2,10 +2,10 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <btcsignals.h>
 #include <interfaces/echo.h>
 #include <interfaces/handler.h>
 
-#include <boost/signals2/connection.hpp>
 #include <memory>
 #include <utility>
 

src/init.cpp

@@ -12,6 +12,7 @@
 #include <addrman.h>
 #include <banman.h>
 #include <blockfilter.h>
+#include <btcsignals.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <chainparamsbase.h>
@@ -110,8 +111,6 @@
 #include <sys/stat.h>
 #endif
 
-#include <boost/signals2/signal.hpp>
-
 #ifdef ENABLE_ZMQ
 #include <zmq/zmqabstractnotifier.h>
 #include <zmq/zmqnotificationinterface.h>

src/node/interface_ui.cpp

@@ -4,12 +4,10 @@
 
 #include <node/interface_ui.h>
 
+#include <btcsignals.h>
 #include <util/string.h>
 #include <util/translation.h>
 
-#include <boost/signals2/optional_last_value.hpp>
-#include <boost/signals2/signal.hpp>
-
 using util::MakeUnorderedList;
 
 CClientUIInterface uiInterface;

src/node/interfaces.cpp

@@ -5,6 +5,7 @@
 #include <addrdb.h>
 #include <banman.h>
 #include <blockfilter.h>
+#include <btcsignals.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <common/args.h>
@@ -69,8 +70,6 @@
 #include <optional>
 #include <utility>
 
-#include <boost/signals2/signal.hpp>
-
 using interfaces::BlockRef;
 using interfaces::BlockTemplate;
 using interfaces::BlockTip;

src/noui.cpp

@@ -5,15 +5,13 @@
 
 #include <noui.h>
 
+#include <btcsignals.h>
 #include <logging.h>
 #include <node/interface_ui.h>
 #include <util/translation.h>
 
 #include <string>
 
-#include <boost/signals2/connection.hpp>
-#include <boost/signals2/signal.hpp>
-
 /** Store connections so we can disconnect them when suppressing output */
 boost::signals2::connection noui_ThreadSafeMessageBoxConn;
 boost::signals2::connection noui_ThreadSafeQuestionConn;

src/qt/bitcoin.cpp

@@ -6,6 +6,7 @@
 
 #include <qt/bitcoin.h>
 
+#include <btcsignals.h>
 #include <chainparams.h>
 #include <common/args.h>
 #include <common/init.h>
@@ -44,7 +45,6 @@
 #include <wallet/types.h>
 #endif // ENABLE_WALLET
 
-#include <boost/signals2/connection.hpp>
 #include <chrono>
 #include <memory>
 

src/wallet/scriptpubkeyman.h

@@ -6,6 +6,7 @@
 #define BITCOIN_WALLET_SCRIPTPUBKEYMAN_H
 
 #include <addresstype.h>
+#include <btcsignals.h>
 #include <common/messages.h>
 #include <common/signmessage.h>
 #include <common/types.h>
@@ -23,8 +24,6 @@
 #include <wallet/walletdb.h>
 #include <wallet/walletutil.h>
 
-#include <boost/signals2/signal.hpp>
-
 #include <functional>
 #include <optional>
 #include <unordered_map>

src/wallet/wallet.h

@@ -7,6 +7,7 @@
 #define BITCOIN_WALLET_WALLET_H
 
 #include <addresstype.h>
+#include <btcsignals.h>
 #include <consensus/amount.h>
 #include <interfaces/chain.h>
 #include <interfaces/handler.h>
@@ -51,8 +52,6 @@
 #include <utility>
 #include <vector>
 
-#include <boost/signals2/signal.hpp>
-
 class CKey;
 class CKeyID;
 class CPubKey;