Issue: FUNCTION-TYPE-REST-LIST-ELEMENT

["Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>]

Rather than introduce some godawful kludge for declaring the type of
&rest lists (only), we should probably try to clean up the inadequacies
of the LIST data-type specification.  There should be some long-form
declaration for LIST that allows you to declare the element-type and
length, similar to the declarations for vectors.

We might or might not want to add a "true list" data type at the same
time.  A "true list" is finite in the CDR direction and terminates in
NIL.  I can forsee some arguments about whether LIST in a declaration
should mean "true list", or whetehr we should give a new name to true
lists.

This is just a trial balloon -- if there is some enthusiasm for this
idea, I'll turn it into a real proposal.  If not, we can go back to
discussing kludges for indicating the element-type in an &REST list.

-- Scott