Chapter 15 and 16 are the last ones of the Implementation part of the book.

Chapter 15 introduces the tools on the UNIX programming environment.
It touches again in the topic of editors, this time especially on Vi(m) and Emacs.

Then, it's introduced the code generators lex and yacc (and their relatives to other languages).
I didn't know that yacc predates structs in C, nor that structs were added later to the language.

I have no knowledge of makefile generators. I use plain makefiles while trying to make them portable, if necessary adding a config.mk file to tune the rules. Four makefile generators are listed: X11 makedepend and imake, and GNU autoconf and automake. I have used none of them.

On the version control topic, it lists the classic UNIX vcs: SCCS, RCS and CVS. Both Git and Mercurial, the most common vcs in use today, are not listed. They were both released in 2005, and the book was published in 2003.

Chapter 16 is about code reuse and the benefits of open source software.
It covers topics such as licensing, documentation, and where to look for other's code (of the places listed, only sourceforge still exists, and it is losing space to github and other git services).