replaceable - check if object is replaceable
int replaceable(object, void | string *func);
string *func defaults to ({ "create", "__INIT" }) and contains a list of
functions which may be ignored for checking
checks if object defines any functions itself (beside create)
returns 1 if no and object is not simul_efun object and not ???
0 otherwise
replace_program(3), query_replaced_program(3)