(info, html): Implement.

(all): Depend on info.

Flatten info directory.  This undoes the move to one subdirectory per
chapter, which was done during Empire 2.  The structure doesn't buy us
much, as the info name space is flat, and it complicates makefiles.

Overhaul info.pl:
- It now wants to run in the root of the build tree.
- Information on source files and subjects is now stored in makefiles,
  thus info.pl no longer picks up random junk from the file system.
- Clean up Perl anachronisms, in particular use subroutine arguments and
  results rather than global variables where convenient.
- Change format of diagnostics to the common format used by GNU tools,
  so that Emacs and the like can parse it.
- Catch missing .SA.
- When creating a new subject file, cowardly refuse to overwrite an
  existing file.
- Subject files contain topics sorted by chapter, then by name.  The
  order of chapters used to depend on how Perl sorts hash keys.  Fix
  it.

info/headlines.t

@@ -0,0 +1,19 @@
+.TH Command HEADLINES
+.NA headlines "Summarize the weeks events (part of \*Qnews\*U)"
+.LV Expert
+.SY "headlines [days]"
+The headlines command lets you read just the important,
+subjective, summary part of the news
+without boring you with the confusing details.
+.s1
+If you include a number in the command,
+it will print headlines based on the news from that many previous days.
+.s1
+The headline \*QRelative Calm Prevails\*U appears
+whenever the reporters haven't been able to dig up
+any interesting tidbits to give the news analysts.
+.s1
+The headlines are produced by the editorial staff of the
+Empire News who are solely responsible for their lack of content.
+.s1
+.SA "newspaper, Communication"