Merge pull request fffaraz#711 from webfolderio/master

Added iup gui library

README.md

@@ -374,6 +374,7 @@ A curated list of awesome C++ (or C) frameworks, libraries, resources, and shiny
 * [GTK+](http://www.gtk.org/) - A multi-platform toolkit for creating graphical user interfaces. [LGPL]
 * [gtkmm](http://www.gtkmm.org/en/) - The official C++ interface for the popular GUI library GTK+. [LGPL]
 * [imgui](https://github.com/ocornut/imgui) - Immediate Mode Graphical User Interface with minimal dependencies. [MIT]
+* [iup](https://www.tecgraf.puc-rio.br/iup) - Multi-platform toolkit for building graphical user interfaces. [MIT]
 * [libRocket](http://librocket.com/) - libRocket is a C++ HTML/CSS game interface middleware. [MIT]
 * [libui](https://github.com/andlabs/libui) - Simple and portable (but not inflexible) GUI library in C that uses the native GUI technologies of each platform it supports. [MIT]
 * [MyGUI](http://mygui.info/) - Fast, flexible and simple GUI. [MIT]