Generalize list(seq) to work with iterators. This also generalizes list()

to no longer insist that len(seq) be defined.
NEEDS DOC CHANGES.
This is meant to be a model for how other functions of this ilk (max,
filter, etc) can be generalized similarly.  Feel encouraged to grab your
favorite and convert it!
Note some cute consequences:
    list(file) == file.readlines() == list(file.xreadlines())
    list(dict) == dict.keys()
    list(dict.iteritems()) = dict.items()
    list(xrange(i, j, k)) == range(i, j, k)

Lib/test/test_iter.py

@@ -243,4 +243,36 @@ class TestCase(unittest.TestCase):
             except OSError:
                 pass
 
+    # Test list()'s use of iterators.
+    def test_builtin_list(self):
+        self.assertEqual(list(SequenceClass(5)), range(5))
+        self.assertEqual(list(SequenceClass(0)), [])
+        self.assertEqual(list(()), [])
+        self.assertEqual(list(range(10, -1, -1)), range(10, -1, -1))
+
+        d = {"one": 1, "two": 2, "three": 3}
+        self.assertEqual(list(d), d.keys())
+
+        self.assertRaises(TypeError, list, list)
+        self.assertRaises(TypeError, list, 42)
+
+        f = open(TESTFN, "w")
+        try:
+            for i in range(5):
+                f.write("%d\n" % i)
+        finally:
+            f.close()
+        f = open(TESTFN, "r")
+        try:
+            self.assertEqual(list(f), ["0\n", "1\n", "2\n", "3\n", "4\n"])
+            f.seek(0, 0)
+            self.assertEqual(list(f.xreadlines()),
+                             ["0\n", "1\n", "2\n", "3\n", "4\n"])
+        finally:
+            f.close()
+            try:
+                unlink(TESTFN)
+            except OSError:
+                pass
+
 run_unittest(TestCase)