Add link for pdf and zipped html for a C book (EbookFoundation#2532)

Include downloads link for a zipped html and pdf versions of a C book.

free-programming-books.md

@@ -855,7 +855,7 @@
 
 ### C
 
-* [A Tutorial on Pointers and Arrays in C](http://home.netcom.com/~tjensen/ptr/pointers.htm)
+* [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
 * [Build Your Own Lisp](http://www.buildyourownlisp.com)