Two things: 1) set flags in copy properly; make mp_map_init() not be too
smart and do something with requested alloc size. Policy of using prime
numbers for alloc size is high-level policy which should be applied at
corresponding high levels. Low-level functions should just do what they're
asked to, because they don't have enough context to be smarter than that.
For example, munging with alloc size of course breaks dict copying (as
changing sizes requires rehashing).

On x64, native emitter now passes 70 of the tests.

Also add command line option to unix port to select emitter.

Based on the discussion in #433. mp_load_attr() is critical-path function,
so any extra check will slowdown any script. As supporting default val
required only for getattr() builtin, move correspending implementation
there (still as a separate function due to concerns of maintainability
of such almost-duplicated code instances).

This is to reduce ROM usage.  stream_p is used in file and socket types
only (at the moment), so seems a good idea to make the protocol
functions a pointer instead of the actual structure.

It saves 308 bytes of ROM in the stmhal/ port, 928 in unix/.

This makes isinstance(X, object) and issubclass(X, object) true for all
X.

Finishes addressing issue #424.

In the end this was a very neat refactor that now makes things a lot
more consistent across the py code base.  It allowed some
simplifications in certain places, now that everything is a dict object.

Also converted builtins tables to dictionaries.  This will be useful
when we need to turn builtins into a proper module.

Towards addressing issue #424.

Had a small increase to ROM usage (order 60 bytes).

Implement del

This does not affect code size or performance when debugging turned off.

To address issue #420.

Change pfenv_print_int to take machine_uint_t rather than unsinged in

Allow floating point arguments with %d,i,u,o,x,X formats

py: Support 3-arg getattr() builtin (with default value).

With this change, the following works:

>>> print('%#x' % 0x1234567890abcdef)
0x1234567890abcdef

Hash table can now be completely full (ie now NULL entry) before a
resize is triggered.  Use sentinel value to indicate delete entry in the
table.

map: When removing a key, don't NULL the entry, but mark as deleted.

Quite natural to have d[int] = handle_int .