bpo-44206: Add a version number to dictionary keys (GH-26333)

* Store log2(size) instead of size in dict-keys.

* Use enum instead of function pointer to record kind of keys.

* Add version number to dict keys.

Tools/gdb/libpython.py

@@ -730,7 +730,7 @@ class PyDictObjectPtr(PyObjectPtr):
 
     def _get_entries(self, keys):
         dk_nentries = int(keys['dk_nentries'])
-        dk_size = int(keys['dk_size'])
+        dk_size = 1<<int(keys['dk_log2_size'])
         try:
             # <= Python 3.5
             return keys['dk_entries'], dk_size