Add import_function method to test.test_support, and modify a number of

tests that expect to be skipped if imports fail or functions don't
exist to use import_function and import_module.  The ultimate goal is
to change regrtest to not skip automatically on ImportError.  Checking
in now to make sure the buldbots don't show any errors on platforms
I can't direct test on.

Lib/test/test_crypt.py

@@ -1,6 +1,7 @@
 from test import test_support
 import unittest
-import crypt
+
+crypt = test_support.import_module('crypt')
 
 class CryptTestCase(unittest.TestCase):