[latexrefman] \write, \message, \wlog, \write18

[Hefferon, Jim S.]

I added these.  They prove to be hard, so no doubt I will need to adjust.  Feedback very welcome.

Accordingly I changed the chapter title from Terminal input/output to just Input/output.

I also need to add small bits for \openout and \closeout but this is enough for a commit.

Jim

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https://en.wikipedia.org/wiki/Cluster_B_personality_disorders