DG Scripts bug fixes (#44)

* Increase ID space

DG Scripts uses tiny idspace that results in wacky bugs when the mud is
running too long.

* Overhaul script ids

All references to GET_ID(ch/obj) were removed and replaced by
char_script_id() and obj_script_id(), which don’t assign ids until they
are needed. The ch->id and obj->id variable names were changed to
script_id to prevent accidental errors for future programmers. This
change greatly increases how long the mud can run before it runs out of
ID space.

* Fix extraction count

This prevents an error log where it has over-counted the extractions
pending. It now behaves correctly when the same mob is %purge%’d or
extract_char()’d twice.

src/utils.h

@@ -537,7 +537,8 @@ do                                                              \
 /** Unique ID of ch. */
 #define GET_IDNUM(ch)	  ((ch)->char_specials.saved.idnum)
 /** Returns contents of id field from x. */
-#define GET_ID(x)         ((x)->id)
+/** Warning: GET_ID is deprecated and you should use char_script_id, obj_script_id, room_script_id */
+/** #define GET_ID(x)         ((x)->id) */
 /** Weight carried by ch. */
 #define IS_CARRYING_W(ch) ((ch)->char_specials.carry_weight)
 /** Number of items carried by ch. */