issue COMPILE-ENVIRONMENT-CONSISTENCY, version 4

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

All the things I didn't like in version 3 have been fixed.
I would favor COMPILE-ENVIRONMENT-CONSISTENCY:CLARIFY if one change
were made.  The proposal says:

  Except where some other behavior is explicitly stated, when
  the compiletime and runtime definitions are different, it is
  unspecified which will prevail within the compiled code.

This means that either the compiletime or the runtime definition
will prevail, but nothing else can happen.  It must also be
permissible to signal an error complaining about the discrepancy.