Fix of Boost 1.79 deprecated boost::filesystem::ofstream #8238

Replacing boost::filesystem::fstream with boost::nowide::fstream
variants with the unfortunate cost of string path conversion on Windows
from 16 bits to UTF8 and back to 16 bits.

Unfortunately we cannot use std::filesystem yet as it is missing
on older MACs and because the interface is crooked minefield on Windows
see microsoft/STL#909

src/hints/HintsToPot.cpp

@@ -9,7 +9,7 @@
 
 bool write_to_pot(boost::filesystem::path path, const std::vector<std::pair<std::string, std::string>>& data)
 {
-	boost::filesystem::ofstream file(std::move(path), std::ios_base::app);
+	boost::nowide::ofstream file(path.string(), std::ios_base::app);
 	for (const auto& element : data)
 	{
 		//Example of .pot element 

src/libslic3r/Preset.cpp

@@ -84,7 +84,7 @@ ConfigFileType guess_config_file_type(const ptree &tree)
 VendorProfile VendorProfile::from_ini(const boost::filesystem::path &path, bool load_all)
 {
     ptree tree;
-    boost::filesystem::ifstream ifs(path);
+    boost::nowide::ifstream ifs(path.string());
     boost::property_tree::read_ini(ifs, tree);
     return VendorProfile::from_ini(tree, path, load_all);
 }

src/slic3r/GUI/HintNotification.cpp

@@ -14,12 +14,14 @@
 #include "libslic3r/Config.hpp"
 #include "libslic3r/PrintConfig.hpp"
 
+#include <map>
+
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/nowide/fstream.hpp>
 #include <boost/log/trivial.hpp>
 #include <boost/property_tree/ini_parser.hpp>
-#include <map>
+
 #include <cereal/archives/binary.hpp>
 #include <cereal/types/string.hpp>
 #include <cereal/types/vector.hpp>
@@ -65,7 +67,7 @@ inline void push_style_color(ImGuiCol idx, const ImVec4& col, bool fading_out, f
 
 void write_used_binary(const std::vector<std::string>& ids)
 {
-	boost::filesystem::ofstream file((boost::filesystem::path(data_dir()) / "cache" / "hints.cereal"), std::ios::binary);
+	boost::nowide::ofstream file((boost::filesystem::path(data_dir()) / "cache" / "hints.cereal").string(), std::ios::binary);
 	cereal::BinaryOutputArchive archive(file);
 		HintsCerealData cd { ids };
 	try
@@ -84,7 +86,7 @@ void read_used_binary(std::vector<std::string>& ids)
 		BOOST_LOG_TRIVIAL(warning) << "Failed to load to hints.cereal. File does not exists. " << path.string();
 		return;
 	}
-	boost::filesystem::ifstream file(path);
+	boost::nowide::ifstream file(path.string());
 	cereal::BinaryInputArchive archive(file);
 	HintsCerealData cd;
 	try