Can now have null bytes in strings.  Can define ROM qstrs per port using
qstrdefsport.h

CMSIS V3.01 -> V3.20. Now in stm/cmsis to keep separate from ST
libraries.

Creating of classes (types) and instances is much more like CPython now.
You can use "type('name', (), {...})" to create classes.

A big change.  Micro Python objects are allocated as individual structs
with the first element being a pointer to the type information (which
is itself an object).  This scheme follows CPython.  Much more flexible,
not necessarily slower, uses same heap memory, and can allocate objects
statically.

Also change name prefix, from py_ to mp_ (mp for Micro Python).