[R6RS] Enumerations proposal pre-draft

[William D Clinger]

> OK.  Would it be an acceptable tweak to add an operand to
> `define-enum-type' like so:

That would be okay with me.  With that tweak, the value of
an enum type would seem to be as a finite universe of symbols
over which efficient operations on sets of symbols could be
defined.  I see considerable value in that.

It seems like a good idea for a SRFI, however, not something
we need to put into the R6RS.  That's just my opinion, of
course.

Will