Test cases from Cowlishaw, v2.57. All are pased cleanly.
diff --git a/Lib/test/decimaltestdata/logb.decTest b/Lib/test/decimaltestdata/logb.decTest
index 577f7a4..a672206 100644
--- a/Lib/test/decimaltestdata/logb.decTest
+++ b/Lib/test/decimaltestdata/logb.decTest
@@ -17,7 +17,7 @@
-- IBM UK, PO Box 31, Birmingham Road, Warwick CV34 5JL, UK --
-- mfc@uk.ibm.com --
------------------------------------------------------------------------
-version: 2.56
+version: 2.57
-- This emphasises the testing of notable cases, as they will often
-- have unusual paths (especially the 10**n results).