[PATCH] build book with pdflatex

[Qian Yun]

I've updated
https://github.com/oldk1331/fricas/commits/new-ps-book/
to
https://github.com/oldk1331/fricas/commit/d88925e40c7aa14c776d7b2c99d1fc8483a57d27

This enables build of the book with pdflatex.

Together with previous commit "build with ps image",
these two commits removes almost 113K lines of ps code.

I've added 22 png files, total size 356KB.

As I said in the other thread, Chapter 14 needs some
modifications before this patch goes in.

This is just the first attempt, comments welcome.

- Qian