Move sstruct under fontTools.misc

Our footprint in the Python module namespace is all under
fontTools now.  User code importing sstruct should be updated
to say "from fontTools.misc import sstruct".
diff --git a/Lib/fontTools/cffLib.py b/Lib/fontTools/cffLib.py
index 719a88b..dd0112c 100644
--- a/Lib/fontTools/cffLib.py
+++ b/Lib/fontTools/cffLib.py
@@ -4,7 +4,8 @@
 # $Id: cffLib.py,v 1.34 2008-03-07 19:56:17 jvr Exp $
 #
 
-import struct, sstruct
+import struct
+from fontTools.misc import sstruct
 import string
 from fontTools.misc import psCharStrings
 from fontTools.misc.textTools import safeEval