This allows keyword maps to be created directly from stack data.

mp_map_deinit() finalizes static map, mp_map_free() - dynamic.

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

Added 0 to the list of primes. Funky primes, these.

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).