(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/buy.t

@@ -0,0 +1,36 @@
+.TH Command BUY
+.NA buy "Purchase commodities from the world market"
+.LV Expert
+.SY "buy <ITEM> <LOT#> <BID/UNIT> <DEST>"
+The buy command allows nations to purchase commodities
+on the open market.
+Not all commodities can be traded -- notably civilians and military.
+.s1
+It is based on a bidding system, and after the bidding time has passed,
+the transactions are executed, and the highest bidder gets the goods
+(maybe.)  If there are no bidders once the time passes, the goods stay
+on the market and the first bidder will get them.
+.s1
+Typical output looks like:
+.EX buy food
+.NF
+
+     Empire Market Report
+   Wed Mar 13 14:26:26 1996
+ lot  high bid  by  time left  owner  item  amount  sector
+ ---  --------  --  ---------  -----  ----  ------  ------
+   0  $  10.00   1   0.00 hrs  (  1)   f        10  
+   1  $   1.00   1   0.00 hrs  (  1)   f        10  
+
+Looks just like Christmas at K-mart, doesn't it!
+
+Which lot are you bidding on: 1
+How much per unit: 2
+destination sector : 3,1
+Your bid is being considered.
+.FI
+.s1
+In addition, the \*Qdestination sector\*U must be a warehouse or harbor,
+and must be greater than 60% efficient to receive commodities.
+.s1
+.SA "reset, sell, market, Commerce"