Function set_for_sale:
Defined in module m_vendor (file: /std/modules/m_vendor.c)

Set the array of object names which this living object is willing to sell.
set_for_sale(1) means everything is for sale.  set_for_sale(0) means nothing
is.  If a function is passed it will get the object to sell as argument.
If a single string is returned it will be used as error message.

Prototype:
void set_for_sale(mixed x);
