Standardize all core and obj functions with relative coords

This is a large iteration on a previous implementation of making
nh.getmap() parse its coordinates as relative to the last defined map or
room rather than absolute to the entire level. Now, everything in the
nh.* and obj.* functions interprets coords as relative rather than
absolute. (By default; if no map or room has been defined, or if the lua
code is executing after level creation is done, they will interpret the
coordinates as absolute).

The general motivation is basically the same - routines that use
absolute coordinates are difficult to use in level creation routines,
because then the designer has to remember to convert the relative
coordinate to an absolute one (and that was impossible before
nh.abscoord was added, particularly in themed rooms). And once
nh.getmap() takes relative coordinates, it would be very strange to have
all the other functions (setting timers, burying objects, etc) remain
with absolute ones.

In a couple places, code is changed to account for coordinates that are
relative to a *room* (which uses g.coder->croom->[lx,ly] as an offset,
instead of relative to a *map*, which uses [xstart,ystart].
Specifically, selection.iterate did not account for this, and without
this the ice themed room timer was not being started in the proper
place.

All tests are updated to respect the new behavior. Most of the modified
functions are not actually used anywhere in level files; the one
exception is starting a timer in a themed room, and that has been
adjusted.

Documentation updated as well to clarify when various things are tossing
around relative and absolute coordinates, both in comments and in
lua.adoc.

src/nhlua.c

@@ -172,7 +172,7 @@ void
 nhl_error(lua_State *L, const char *msg)
 {
     lua_Debug ar;
-    char buf[BUFSZ];
+    char buf[BUFSZ*2];
 
     lua_getstack(L, 1, &ar);
     lua_getinfo(L, "lS", &ar);
@@ -389,6 +389,7 @@ nhl_gettrap(lua_State *L)
     }
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
             struct trap *ttmp = t_at(x,y);
@@ -439,7 +440,8 @@ nhl_deltrap(lua_State *L)
     }
     x = (coordxy) lx;
     y = (coordxy) ly;
-    
+    cvt_to_abscoord(&x, &y);
+
     if (isok(x, y)) {
         struct trap *ttmp = t_at(x,y);
 
@@ -452,6 +454,11 @@ nhl_deltrap(lua_State *L)
 /* get parameters (XX,YY) or ({ x = XX, y = YY }) or ({ XX, YY }),
    and set the x and y values.
    return TRUE if there are such params in the stack.
+   Note that this does not adjust the values of x and y at all from what is
+   specified in the level file; so, it returns absolute coordinates rather than
+   map-relative coordinates. Callers of this function must decide if they want
+   to interpret the values as absolute or as map-relative, and adjust
+   accordingly.
  */
 boolean
 nhl_get_xy_params(lua_State *L, lua_Integer *x, lua_Integer *y)
@@ -487,23 +494,9 @@ nhl_getmap(lua_State *L)
         nhl_error(L, "Incorrect arguments");
         return 0;
     }
-    if (g.in_mklev) {
-        /* xstart and ystart are set by the des.map() command to give
-         * coordinates relative to the 0,0 of that map. It can be quite useful
-         * to check what terrain is on a given space. But without compensating
-         * for the change in xstart and ystart here, this will lead to results
-         * like des.terrain(4,6,'L') and then nh.getmap(4,6) not being lava.
-         *
-         * Only valid during mklev, because xstart and ystart are not saved
-         * with the level and can change during the level creating process when
-         * additional des.map() are executed. They will not necessarily be the
-         * same later. */
-        x += g.xstart;
-        y += g.ystart;
-    }
-
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
             char buf[BUFSZ];
@@ -1177,6 +1170,7 @@ nhl_timer_has_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
         when = spot_time_expires(x, y, timertype);
@@ -1205,6 +1199,7 @@ nhl_timer_peek_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y))
         when = spot_time_expires(x, y, timertype);
@@ -1230,6 +1225,7 @@ nhl_timer_stop_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y))
         spot_stop_timers(x, y, timertype);
@@ -1254,6 +1250,7 @@ nhl_timer_start_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y)) {
         long where = ((long) x << 16) | (long) y;