Test cases from Cowlishaw, v2.57. All are pased cleanly.
diff --git a/Lib/test/decimaltestdata/ddLogB.decTest b/Lib/test/decimaltestdata/ddLogB.decTest
index f18fd5e..99a3843 100644
--- a/Lib/test/decimaltestdata/ddLogB.decTest
+++ b/Lib/test/decimaltestdata/ddLogB.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
precision: 16
maxExponent: 384