Add the 'bool' type and its values 'False' and 'True', as described in

PEP 285.  Everything described in the PEP is here, and there is even
some documentation.  I had to fix 12 unit tests; all but one of these
were printing Boolean outcomes that changed from 0/1 to False/True.
(The exception is test_unicode.py, which did a type(x) == type(y)
style comparison.  I could've fixed that with a single line using
issubtype(x, type(y)), but instead chose to be explicit about those
places where a bool is expected.

Still to do: perhaps more documentation; change standard library
modules to return False/True from predicates.

Lib/doctest.py

@@ -545,19 +545,19 @@ def is_private(prefix, base):
     does not both begin and end with (at least) two underscores.
 
     >>> is_private("a.b", "my_func")
-    0
+    False
     >>> is_private("____", "_my_func")
-    1
+    True
     >>> is_private("someclass", "__init__")
-    0
+    False
     >>> is_private("sometypo", "__init_")
-    1
+    True
     >>> is_private("x.y.z", "_")
-    1
+    True
     >>> is_private("_x.y.z", "__")
-    0
+    False
     >>> is_private("", "")  # senseless but consistent
-    0
+    False
     """
 
     return base[:1] == "_" and not base[:2] == "__" == base[-2:]