[Freeciv-Dev] remove nearest_real_pos uses (PR#1211)

[jdorje@xxxxxxxxxxxxxxxxxxxxx]

The attached patch removes two unnecessary (incorrect AFAICT) uses of 
nearest_real_pos.
1.  In map_get_player_tile(), I've replaced the nearest_real_pos call 
with a CHECK_MAP_POS check (included in map_inx).  I haven't verified 
that all calls to the code are safe, but (1) the error message that is 
currently displayed for non-real tiles is never shown and (2) 
extensively running autogames has yet to turn up a failed assert.
Note that Ross's corecleanups return NULL in the case of a non-real map 
position, but this isn't desired IMO and isn't feasible at this time 
(since it would require converting all uses to check the return value, 
which they currently do not do).
2.  In auto_settler_do_goto(), it has been simply replaced by 
CHECK_MAP_POS.  Here I've scanned all the calls to the function, and it 
looks like they should all pass Good coordinates.  Again there have been 
no failed assertions in my autogames.
Note that Ross's corecleanups handle this incorrectly, as they call 
normalize_map_pos on the coordinates and ignore the return value 
(verboten!  Ross, you should know better!).  This will result in 
unpredictible behavior if non-real coordinates are ever passed in; most 
likely (and hopefully) a failed CHECK_MAP_POS check later on when the 
coordinates are actually used.
If this patch is applied, the only remaining nearest_real_pos use will 
be in map_pos_to_canvas_pos in mapview_common.  If one of these places 
does need to use nearest_real_pos (which seems inconceivable), a comment 
should be added explaining why.
jason