add vga programming book (#2876)

free-programming-books.md

@@ -881,6 +881,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### C
 
+* [256-Color VGA Programming in C](http://www.brackeen.com/vga/) - David Brackeen
 * [A Tutorial on Pointers and Arrays in C](http://home.netcom.com/~tjensen/ptr/pointers.htm) - Ted Jensen [(PDF, Zipped HTML)](http://pweb.netcom.com/~tjensen/ptr/cpoint.htm)
 * [Beej's Guide to C Programming](http://beej.us/guide/bgc/) - B. Hall
 * [Beej's Guide to Network Programming - Using Internet Sockets](http://beej.us/guide/bgnet/) - B. Hall
@@ -903,7 +904,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [The little book about OS development](http://littleosbook.github.io) - Erik Helin, Adam Renberg
 * [The New C Standard - An Economic and Cultural commentary (2009)](http://www.knosof.co.uk/cbook/cbook.html) - Derek M. Jones (PDF)
 * [TONC GBA Programming - Game Boy Advance Development](http://www.coranac.com/tonc/text/toc.htm)
-* [Using C on the UNIX System](http://www.bitsinthewind.com/about-dac/publications/using-c-on-the-unix-system) - David A. Curry
 
 
 ### C Sharp
@@ -1159,6 +1159,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 * [Books and Articles from FreeBSD Site](http://www.freebsd.org/docs/books.html)
 * [The Complete FreeBSD](http://www.lemis.com/grog/Documentation/CFBSD/)
+* [Using C on the UNIX System](http://www.bitsinthewind.com/about-dac/publications/using-c-on-the-unix-system) - David A. Curry
 
 
 ### Git
@@ -1662,6 +1663,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Ubuntu Pocket Guide and Reference](http://www.ubuntupocketguide.com/index_main.html)
 * [Ubuntu Server Guide](https://help.ubuntu.com/16.04/serverguide/serverguide.pdf) (PDF)
 * [Understanding the Linux Virtual Memory Manager](https://www.kernel.org/doc/gorman/) - Mel Gorman (HTML, PDF)
+* [UNIX Systems Programming for SVR4](http://www.bitsinthewind.com/about-dac/publications/unix-systems-programming) - David A. Curry
 * [Upstart Intro, Cookbook and Best Practises](http://upstart.ubuntu.com/cookbook/)
 * [What Every Programmer Should Know About Memory](http://www.akkadia.org/drepper/cpumemory.pdf) (PDF)