Important usability fix in itertools documentation.

Doc/lib/libitertools.tex

@@ -348,15 +348,15 @@ from building blocks.
 
 >>> def all(pred, seq):
 ...     "Returns True if pred(x) is True for every element in the iterable"
-...     return not nth(ifilterfalse(pred, seq), 0)
+...     return False not in imap(pred, seq)
 
 >>> def some(pred, seq):
 ...     "Returns True if pred(x) is True at least one element in the iterable"
-...     return bool(nth(ifilter(pred, seq), 0))
+...     return True in imap(pred, seq)
 
 >>> def no(pred, seq):
 ...     "Returns True if pred(x) is False for every element in the iterable"
-...     return not nth(ifilter(pred, seq), 0)
+...     return True not in imap(pred, seq)
 
 >>> def padnone(seq):
 ...     "Returns the sequence elements and then returns None indefinitely"