/=V should allow integer bounds to be restricted

 Now

  (let ((a (an-integer-betweenv 1 2))
        (b (an-integer-betweenv 1 2)))
    (assert! (/=v a b))
    (assert! (=v a 1))
    (value-of b)) ; => 2

 whereas in classic Screamer the plain assertion isn't
 enough to learn the result.
Merge branch 'master' into dev
Merge branch 'master' into dev
tweak brave new /=V

 Mention the range-restriction in the docstring.

 Take care to only adjust ranges of integers, but simultaneously allow
 (ASSERT! (/=V [integer 1:3] 3.0)) to restrict the variable to 1:2.
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev
simplify ALL-DIFFERENTV from the Zebra example

  Given the improved /=V, this is actually faster.
ATTACH-NOTICER! can now attach the same noticer to multiple things

  Micro-optimizes some things a bit, as we don't now call
  the same noticer twice for eg. (ASSERT! (=V X Y)).
Merge branch 'master' into dev

Conflicts:
	tests.lisp
Merge branch 'master' into dev
delete UNWIND-TRAIL

  I don't see any safe way for users to call it without being in danger of
  messing up Screamer's internal state.
Merge branch 'master' into dev
/=V should allow integer bounds to be restricted

 Now

  (let ((a (an-integer-betweenv 1 2))
        (b (an-integer-betweenv 1 2)))
    (assert! (/=v a b))
    (assert! (=v a 1))
    (value-of b)) ; => 2

 whereas in classic Screamer the plain assertion isn't
 enough to learn the result.
tweak brave new /=V

 Mention the range-restriction in the docstring.

 Take care to only adjust ranges of integers, but simultaneously allow
 (ASSERT! (/=V [integer 1:3] 3.0)) to restrict the variable to 1:2.
simplify ALL-DIFFERENTV from the Zebra example

  Given the improved /=V, this is actually faster.
ATTACH-NOTICER! can now attach the same noticer to multiple things

  Micro-optimizes some things a bit, as we don't now call
  the same noticer twice for eg. (ASSERT! (=V X Y)).
delete UNWIND-TRAIL

  I don't see any safe way for users to call it without being in danger of
  messing up Screamer's internal state.
Merge branch 'wip' (early part) into dev