Issue #25914: Fixed and simplified OrderedDict.__sizeof__.

diff --cc Lib/test/test_ordered_dict.py
Simple merge

diff --cc Misc/NEWS
index 0d9c7dd3a5a110aa6d8412577e605304749edf21,3257aa4a033759aac223571da19b6251d46010ea..4a94f76c2360b1e77be204ee9ba2324c5c3b74e8
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -115,22 -28,10 +115,24 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #25914: Fixed and simplified OrderedDict.__sizeof__.
+ 
 +- Issue #25869: Optimized deepcopying ElementTree; it is now 20 times faster.
 +
 +- Issue #25873: Optimized iterating ElementTree.  Iterating elements
 +  Element.iter() is now 40% faster, iterating text Element.itertext()
 +  is now up to 2.5 times faster.
 +
  - Issue #25902: Fixed various refcount issues in ElementTree iteration.
  
 +- Issue #22227: The TarFile iterator is reimplemented using generator.
 +  This implementation is simpler that using class.
 +
 +- Issue #25638: Optimized ElementTree.iterparse(); it is now 2x faster.
 +  Optimized ElementTree parsing; it is now 10% faster.
 +
 +- Issue #25761: Improved detecting errors in broken pickle data.
 +
  - Issue #25717: Restore the previous behaviour of tolerating most fstat()
    errors when opening files.  This was a regression in 3.5a1, and stopped
    anonymous temporary files from working in special cases.

diff --cc Objects/dictobject.c
Simple merge