(svn r1407) -Codechange: changed a lot around _stations, _vehicles, _towns and _industries

(in prepare of dynamic arrays):
  - DEREF_XXX is changed into GetXXX
  - All direct call are directed via GetXXX
  - struct Industry has now an index-field
  - ENUM'd some stuff
  - Replaced home built loops with FOR_ALL_XXX
  - Added _stations_size, _vehicles_size, ... which gives the length of the
    array (which will be dynamic in the near future)
  - Changed lengtof(XXX) to _XXX_size (e.g. _stations_size)
  - Removed all endof(XXX) (because mostly it was part of a FOR_ALL_XXX)
  - Made the sort-functions of all 4 dynamic
  - Made all 4 Initialize functions more of the same
  - Some minor tab-fixing and stuff
  (tnx to Tron for proof-reading my 100kb patch ;))

  Note for all: please do NOT directly call _stations, _vehicles, _towns and
  _industries, but use the right wrapper to access them. Thank you.
  Ps: please also do not use 'v++', where v is of type Vehicle *.

town.h

@@ -91,10 +91,19 @@ enum {
 
 bool CheckforTownRating(uint tile, uint32 flags, Town *t, byte type);
 
-#define DEREF_TOWN(i) (&_towns[i])
-#define FOR_ALL_TOWNS(c) for(c=_towns; c != endof(_towns); c++)
-
 VARDEF Town _towns[70];
+VARDEF uint _towns_size;
+
+VARDEF uint16 *_town_sort;
+
+static inline Town *GetTown(uint index)
+{
+	assert(index < _towns_size);
+	return &_towns[index];
+}
+
+#define FOR_ALL_TOWNS(t) for(t = _towns; t != &_towns[_towns_size]; t++)
+
 VARDEF int _total_towns; // For the AI: the amount of towns active
 
 VARDEF bool _town_sort_dirty;