Add the Visual Prolog programming language

See: http://www.visual-prolog.com/

free-programming-books.md

@@ -152,6 +152,7 @@
 * [TypeScript](#typescript)
 * [Unix](#unix)
 * [Vim](#vim)
+* [Visual Prolog](#visual-prolog)
 * [Web Services](#web-services)
 * [Windows 8](#windows-8)
 * [Windows Phone](#windows-phone)
@@ -1668,6 +1669,11 @@ See also [LaTeX](#latex)
 * [Use Vim Like A Pro](https://leanpub.com/VimLikeAPro) *(Leanpub, by Tim Ottinger)*
 
 
+###Visual Prolog
+* [A Beginners' Guide to Visual Prolog](http://wiki.visual-prolog.com/index.php?title=A_Beginners_Guide_to_Visual_Prolog)
+* [Visual Prolog for Tyros](http://wiki.visual-prolog.com/index.php?title=Visual_Prolog_for_Tyros)
+
+
 ###Web Services
 * [RESTful Web Services](http://restfulwebapis.org/RESTful_Web_Services.pdf) (PDF)