__bool__() and __len__() are just the same as __neg__() or __invert__(),
and require efficient dispatching implementation (not requiring search/lookup).
type->unary_op() is just the right choice for this short of adding
standalone virtual method(s) to already big mp_obj_type_t structure.
We still have FAST_[0,1,2] byte codes, but they now just access the
fastn array (before they had special local variables). It's now
simpler, a bit faster, and uses a bit less stack space (on STM at least,
which is most important).
The only reason now to keep FAST_[0,1,2] byte codes is for compressed
byte code size.
Qstr's are now split into a linked-list of qstr pools. This has 2
benefits: the first pool can be in ROM (huge benefit, since we no longer
use RAM for the core qstrs), and subsequent pools use m_new for the next
pool instead of m_renew (thus avoiding a huge single table for all the
qstrs).
Still would be better to use a hash table, but this scheme takes us part
of the way (eventually convert the pools to hash tables).
Also fixed bug with import.
Also improved the way the module code is referenced (not magic number 1
anymore).
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).
