[Bug #1512163] Fix typo.

This change will probably break tests on FreeBSD buildbots, but I'll check in
a fix for that next.
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index bb115e1..3777c8e 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -15,7 +15,7 @@
 import rfc822
 import StringIO
 try:
-    import fnctl
+    import fcntl
 except ImportError:
     fcntl = None