(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/stop.t

@@ -0,0 +1,21 @@
+.TH Command STOP
+.NA stop "Stop sector production"
+.LV Expert
+.SY "stop <SECTS>"
+The stop command orders a sector to stop producing for an update.
+After the update, the sector will return to normal.
+.s1
+The sector will still distribute, etc, but will not gain in efficiency or
+produce anything. Ships, planes, and units in the sector will
+not gain efficiency.
+.s1
+.EX stop 2,0
+.NF
+Wed Jan 20 21:35:34 1993
+PRODUCTION STOPPAGE
+  sect        eff
+   2,0    c  100% will not produce or gain efficiency.
+    1 sector
+.FI
+.s1
+.SA "start, census, Producing, Updates"