Remove fallbacks for boost_filesystem < v3

Minimum boost version was bumped to 1.47.0 in #8920, which
means the configure step won't even pass with older boost.

This version has boost filesystem v3, which means the
(crappy) fallbacks for older versions can go.

src/qt/guiutil.cpp

@@ -37,9 +37,7 @@
 
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
-#if BOOST_FILESYSTEM_VERSION >= 3
 #include <boost/filesystem/detail/utf8_codecvt_facet.hpp>
-#endif
 #include <boost/scoped_array.hpp>
 
 #include <QAbstractItemView>
@@ -67,9 +65,7 @@
 #include <QFontDatabase>
 #endif
 
-#if BOOST_FILESYSTEM_VERSION >= 3
 static boost::filesystem::detail::utf8_codecvt_facet utf8;
-#endif
 
 #if defined(Q_OS_MAC)
 extern double NSAppKitVersionNumber;
@@ -860,7 +856,6 @@ void setClipboard(const QString& str)
     QApplication::clipboard()->setText(str, QClipboard::Selection);
 }
 
-#if BOOST_FILESYSTEM_VERSION >= 3
 boost::filesystem::path qstringToBoostPath(const QString &path)
 {
     return boost::filesystem::path(path.toStdString(), utf8);
@@ -870,18 +865,6 @@ QString boostPathToQString(const boost::filesystem::path &path)
 {
     return QString::fromStdString(path.string(utf8));
 }
-#else
-#warning Conversion between boost path and QString can use invalid character encoding with boost_filesystem v2 and older
-boost::filesystem::path qstringToBoostPath(const QString &path)
-{
-    return boost::filesystem::path(path.toStdString());
-}
-
-QString boostPathToQString(const boost::filesystem::path &path)
-{
-    return QString::fromStdString(path.string());
-}
-#endif
 
 QString formatDurationStr(int secs)
 {

src/test/testutil.cpp

@@ -11,23 +11,5 @@
 #include <boost/filesystem.hpp>
 
 boost::filesystem::path GetTempPath() {
-#if BOOST_FILESYSTEM_VERSION == 3
     return boost::filesystem::temp_directory_path();
-#else
-    // TODO: remove when we don't support filesystem v2 anymore
-    boost::filesystem::path path;
-#ifdef WIN32
-    char pszPath[MAX_PATH] = "";
-
-    if (GetTempPathA(MAX_PATH, pszPath))
-        path = boost::filesystem::path(pszPath);
-#else
-    path = boost::filesystem::path("/tmp");
-#endif
-    if (path.empty() || !boost::filesystem::is_directory(path)) {
-        LogPrintf("GetTempPath(): failed to find temp path\n");
-        return boost::filesystem::path("");
-    }
-    return path;
-#endif
 }

src/wallet/wallet.cpp

@@ -3874,11 +3874,7 @@ bool CWallet::BackupWallet(const std::string& strDest)
                     pathDest /= strWalletFile;
 
                 try {
-#if BOOST_VERSION >= 104000
                     boost::filesystem::copy_file(pathSrc, pathDest, boost::filesystem::copy_option::overwrite_if_exists);
-#else
-                    boost::filesystem::copy_file(pathSrc, pathDest);
-#endif
                     LogPrintf("copied %s to %s\n", strWalletFile, pathDest.string());
                     return true;
                 } catch (const boost::filesystem::filesystem_error& e) {