add newline feature to the text node, add about window with credits, add about menu with submenus

src/util.cpp

@@ -105,6 +105,31 @@ std::vector<std::string> split(const std::string& subject, char d, int max_split
     return ret;
 }
 
+std::string unescape(const std::string& s)
+{
+    std::string res;
+    std::string::const_iterator it = s.begin();
+    while (it != s.end())
+    {
+        char c = *it++;
+        if (c == '\\' && it != s.end())
+        {
+            switch (*it++) {
+            case '\\': c = '\\'; break;
+            case 'n': c = '\n'; break;
+            case 't': c = '\t'; break;
+                // all other escapes
+            default:
+                // invalid escape sequence - skip it. alternatively you can copy it as is, throw an exception...
+                continue;
+            }
+        }
+        res += c;
+    }
+
+    return res;
+}
+
 static const char* gl2str(GLenum err)
 {
     switch (err)