Attached patch is fairly straightforward with only one caveat: instead 
of prefixing unlist_types_without_objects flag with _Py_, I made it 
static.  This may not be the right thing if it is intended to be 
accessible from third party modules (it is not used outside of object.c 
in python code).  I am not sure how it is supposed to be used because it 
appears to be always 0. (Maybe the intent is to change it manually in 
specialized builds or in debugger.)

I am not proposing to move declarations to header files with this patch.  
That change would cause a massive recompile for everyone and if a 
decision is made that globals' declarations belong to header files, this 
should probably be done it one sweep with issue4805 .