Merge refactoring I did when committing r72267 to trunk into the
already committed issue4751 support in py3k r68411.
diff --git a/Doc/library/hashlib.rst b/Doc/library/hashlib.rst
index 955afb8..36f386c 100644
--- a/Doc/library/hashlib.rst
+++ b/Doc/library/hashlib.rst
@@ -105,6 +105,12 @@
    concatenation of all the arguments: ``m.update(a); m.update(b)`` is
    equivalent to ``m.update(a+b)``.
 
+   .. versionchanged:: 2.7
+
+      The Python GIL is released to allow other threads to run while
+      hash updates on data larger than 2048 bytes is taking place when
+      using hash algorithms supplied by OpenSSL.
+
 
 .. method:: hash.digest()