extending DEFSTRUCT

[Dave.Touretzky@C.CS.CMU.EDU]

I support the proposal of Gallagher and Corkill, with one modification:

Instead of *INHIBIT-DEFSTRUCT-PRINTERS*, there should be a variable called
*PRINT-STRUCTURE* that is analagous to *PRINT-ARRAY*.

When *PRINT-STRUCTURE* is T:
  defstructs with their own print functions will use them
  defstructs without prnt functions will print in the #S() notation

When *PRINT-STRUCTURE* in NIL:
  defstructs with their own print functions will use them
  defstructs without their own print function will print in the #<> notation

When *PRINT-STRUCTURE* is :FORCE
  all defstructs print in #S() notation

-- Dave
-------