Still to do:

pybench needs updating to remove a cmp reference;  since the changes 
required for pybench are a little bit more substantial than simple cmp 
replacement, I've broken this out into a separate issue:  issue 4704.

There are many uses of cmp still in the Demos directory.  How much do we 
care?

The documentation in Doc/extending/newtypes.rst needs updating.  I can 
have a go at this, but Georg would almost certainly do a better job.