(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/transport.t

@@ -0,0 +1,32 @@
+.TH Command TRANSPORT
+.NA transport "Move planes or nuclear devices around"
+.LV Basic
+.SY "transport plane <PLANES> <ROUTE|DESTINATION>"
+.SY "transport nuke <SECT> <NUKETYPE> <number> <ROUTE|DESTINATION>"
+The transport command is used to move planes and nuclear devices from
+one sector to another, along the ground.
+.s1
+<ROUTE> is a normal empire path specification. You may also give a
+<DESTINATION> sector on the command line, or at any time while giving
+the route, and empire will use the cheapest path (in terms of mobility)
+from the current sector to the destination sector.
+.s1
+You would move 5 small nukes from 2,0 to 8,0 as follows:
+.EX transport nuke 2,0 small 5 8,0
+.s1
+You could move all planes in wing d to -6,0 as follows:
+.EX transport plane d -6,0
+.s1
+Note that while transporting, you may run into any landmines the
+enemy has left in your sectors. In that case, the planes being
+transported will take damage. See info \*Qlmine\*U for details.
+.s1
+Also, if your enemy has any units on interdiction mission, then the
+planes you're transporting may get hit by them.
+.s1
+Nuclear warheads are transported in heavily armoured vehicles and are
+immune to land mines and interdiction.
+.s1
+See info \*QMobility\*U for the mobility cost to transport planes and nukes.
+.s1
+.SA "arm, move, navigate, nuke, Mobility, Planes, Transportation, Moving"