* map: load / save / generate will properly handle areas beyond game->cur_om,
  load accepts optional *overmap argument to allow creation of additional
  long distance map areas ( for nukes and such ).
* map::loadn: don't iterate vehicles if update_vehicles==false. Skip spoilage check too
* submap: store absolute submap coordinate (as in maps.txt) as x,y,z
* map: store absolute submap coordinate of top-left submap as point abs_sub
* map: getabs(x, y) converts local-to-map tile coordinates to absolute tile
  coordinate (ie, if cur_om() = -1,0 and levx = 1,2, getabs(0,-500) will return
  -4308,-476
* map: getabs: [TEMPORARY/TESTING] perform sanity check that grid[0] and abs_sub agree.
* map: inboundabs(x, y): works with absolute tile coordinates instead of local-top-map
  coordinates
* map: getspawns(x,y); returns std::vector<spawn_point>& for the appropriate submap

* real_coords: fromabs(x, y) will subdivide absolute tile coordinates to standard
  overmap / submap values, ie:
  -4308,-476 = abs_sub: -359,-40, abs_sub_pos: 0,4, abs_om: -1,-1, abs_om_pos: 1,320
  This is the start of refactoring real_coords, which has to loop to take oob values
  into account and doesn't provide abs_om_pos ( submap constrained by overmap limit )
* real_coords: fromomap(omx, omy, suboffsetx, suboffsety) will populate abs_ coordinate
  values based on overmap & relative-to-overmap (unwrapped) overmap pos. Specifically
  for dealing with overmap::draw_overmap:
    point target=cur_om->draw_overmap(this, 0);
    real_coords tgt;
    tgt.fromomap( cur_om->pos().x, cur_om->pos().y, target.x, target.y);
map: Set abs_min/abs_max properly, make inboundsabs(x,y) public
Add stringfmt function for formatting errors
Add small usage of coordinate calculation functions, pending completion of big one.
sync with upstream
map::add_item has optional argument to add to OOB coordinates, by calling map::add_item_anywhere(x, y, z, item, maxitems) which adds to absolute coordinates.
Add regression test debug-menu option + tests for add_item_anywhere as
well as add_item_or_charges. The tests are not really intended for
anything but pre-merge tests, however the menu itself may be useful
for pre-merge testing in the future.
add 'design' and 500ms overhead
Merge commit 'f9073b9' into add_item_oob
add_item_anywhere: drop to existing sub, spawn tmp map for
non-existing subs
add_item*: return success
Merge pull request #11 from atomicdryad/better_map_phase_0.1

map <=> abs coordinate helper functions, long distance generation, add_item oob