Nuprl - Pf iff_imp_equal

1. a:
2. b:
3. a b

a = b

By: OnCls [2;1] BoolCases THEN RWH assert_evalC -1

Generated subgoals:

1 1. False True
2. False True
false = true

2 1. True False
2. True False
true = false

1	1. `False True` 2. `False True` `false = true`
2	1. `True False` 2. `True False` `true = false`