[Freeciv-Dev] Cleaning up gotohand.c (PR#1068)

[Gregory Berkolaiko <gberkolaiko@xxxxxxxxxxx>]

Old subject: Safe paths for triremes.

Since there were no signs that the management of the CVS is going to put
my patch in immediately, I decided to update it, in the meantime.  The
changes from the previous patch: 

* in two places in really_generate_warmap and find_the_shortest_path it
is no longer assumed that RAILROAD cost is zero.  The resulting statement
is ugly due to the legacy from long ago: any IGTER move costs SINGLE_MOVE
on the warmap, not MOVE_COST_ROAD as it should.  I haven't got the
courage to challenge this legacy yet.
* Extensive variable renaming in find_a_direction.  I do really hope that
it makes the code clearer although in some places it is completely over
my head.  Added some comments too, where I know what to say.

! Neither of the changes affects the program flow !

The old parts of the patch are described below:

========================================================================

As was requested about a month ago, I am splitting my warmap patch into a
series of smaller patches.

The first part is mostly cleanup.
Below is the list of features (unfortunately there is no way to comment
the patch in the patch itself):

File gotohand.c:
In really_generate_warmap: 
* removed some comments referring to the code which is not there for
years  
* added some comments (editor, feel free to cut my comments short)
* removed "silence compiler warning" line because there is no compiler
warning anymore
In generate_warmap:
* comments
* fixed buggy check
  if (warmap.warunit == punit && !warmap.cost[punit->x][punit->y])
* removed initializations that do not affect anything
In dir_ok:
* removed dir_ok (sorry guys)
In goto_zoc_ok:
* as was proposed in the comment, changed the code to take into account
where we _really_ came from, not to guess the direction from dir_ok
* changed the comment accordingly
In find_a_direction:
* the previous handling of trireme was pathetic.  changed it to use
is_coast_seen.  NB: it does not mean that triremes are safe: if
find_a_direction is given an unsafe destination it is unlikely to help.
=====================
General remark: 
AI goto has 3 levels
1. Find a destination -- generate_warmap
   takes into account terrain only
2. Find routes to destination -- find_the_shortest_path
   takes into account some info about enemy and ZOC
3. Choose between the routes -- find_a_direction
   final level of detalisation.
=====================
In other places:
* general cleanup of magic numbers
* definition of is_coast_seen

Waiting for your comments,
G.



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