Take care of most of include/*.h. I punted on extern.h.
For both src/*.c and include/*.h, I used mismatched checks of
width > 79 to decide which files to look at and then width > 78
to decide which lines to maybe revise, so I didn't look at a bunch
of the files.
I don't plan to go back and do it right. Shortening lines that are
80 or wider to less than 80 is the significant part. Otherwise
emacs puts a backslash in column 80 and the rest of the line of text
on the next line of the screen, making things harder to read.
This is the version from the Comprehensive C Archive Network, licensed
under the CC0 "No Rights Reserved" Creative Common License.
http://ccodearchive.net/info/isaac.html