Fix save filename newline bug on Linux

src/tools/winutil.linux.cpp

@@ -159,6 +159,11 @@ static std::string runFileDialog(const std::string& file, bool save) {
         if (fgets(buffer, 128, hfile) != NULL)
             filename += buffer;
     }
+
+    // Remove possible unwanted newline included from end of popen() output
+    if (filename[filename.length()-1] == '\n')
+        filename.erase(filename.length()-1);
+
     pclose(hfile);
     return filename;
 }