Make BZ2File's fileobj support easier to use.

The fileobj argument was added during the 3.3 development cycle, so this change
does not break backward compatibility with 3.2.
diff --git a/Misc/NEWS b/Misc/NEWS
index 46f3fd9..1dc0391 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -15,6 +15,9 @@
 Library
 -------
 
+- BZ2File.__init__() now accepts a file object as its first argument, rather
+  than requiring a separate "fileobj" argument.
+
 - gzip.open() now accepts file objects as well as filenames.
 
 - Issue #14992: os.makedirs(path, exist_ok=True) would raise an OSError