present_clone() - finds an object in an inventory based on a file name or
a blueprint


object present_clone(string str)
object present_clone(string str, int n)
object present_clone(string str, object env)
object present_clone(string str, object env, int n)

object present_clone(object obj)
object present_clone(object obj, int n)
object present_clone(object obj, object env)
object present_clone(object obj, object env, int n)


This efun searches the inventory of object <env> (default is
previous_object()) for an object with a specific blueprint.
The blueprint can be specified either by name <str>, or as the same
blueprint as of object <obj>. The matching criteria in both cases is
the load_object(base_name(obj)).

If <n> is given, the <n>th object in <env> is returned (if present),
otherwise the first object matching <str> or <obj>.
If no object in <env> matches the criteria, 0 is returned.


Assume that object 'env' contains the objects /obj/money#8,
/std/weapon#9, /std/weapon#12 and /obj/key in the given order.

| Function call                                    | returns       |
| present_clone("/obj/money", env)                 | /obj/money#8  |
| present_clone("/std/weapon#12", env)             | /std/weapon#9 |
| present_clone(find_object("/obj/money#14"), env) | /obj/money#8  |
| present_clone("/obj/key#18", env)                | /obj/key      |
| present_clone("/std/weapon#12", env, 2)          | /std/weapon#12|
| present_clone("/std/weapon#12", env, 3)          | 0             |