Re: issue CONSTANT-CIRCULAR-COMPILATION, version 4

[Jeff Dalton <jeff%aiai.edinburgh.ac.uk@NSS.Cs.Ucl.AC.UK>]

  Regardless of the disposition of COMPILER-LET, I think the proposal had
  better also say that *dump-circle* is rebound to its current value at least
  during COMPILE-FILE.  That way a source file can (eval-when (compile)
  (setq *dump-circle* t)) if it contains circular structure.

*Dump-circle* is beginning to bother me.  Because users can write
#n= and #n# in source code, they can specify constants that contain
sharing and circularities; and so those constants should be dumped.
I do not think it's reasonable to make the language weaker than the
source notation; and so I don't think *dump-circle* should exist
at all: it should always be as if it were true.