factored out to_hex into the escape_string header file

src/escape_string.cpp

@@ -352,5 +352,17 @@ namespace libtorrent
 		return url.substr(pos, url.find('&', pos) - pos);
 	}
 
+	TORRENT_EXPORT std::string to_hex(std::string const& s)
+	{
+		std::string ret;
+		char* digits = "0123456789abcdef";
+		for (std::string::const_iterator i = s.begin(); i != s.end(); ++i)
+		{
+			ret += digits[((unsigned char)*i) >> 4];
+			ret += digits[((unsigned char)*i) & 0xf];
+		}
+		return ret;
+	}
+
 }