I.e. with its own globals. So, just as for functions, we need to switch
globals when resuming a generator.

Tests in basics (which should probably be renamed to core) should not
rely on float, or import any non-built-in files.  This way these tests
can be run when those features are not available.

All test in basics now pass on the pyboard using stmhal port, except for
string-repr which has some issues with character hex printing.

Fixing the USB problem on stmhal now gets these 2 tests working.

See the `skip_travis_tests` variable. Fixes #495
(also tidied up usage of os.path.basename() function)

Would be good to test this, but need to find a way to optionally not
running it when on travis.

We're not going to implement all the plethora of types in there in C.
Funnily, CPython implements defaultdict in C, and namedtuple in Python.

This is necessary to catch all cases where locals are referenced before
assignment.  We still keep the _0, _1, _2 versions of LOAD_FAST to help
reduced the byte code size in RAM.

Addresses issue #457.

This helps with handling "recursive" imports in sane manner, for example
when foo/__init__.py has something like "from foo import submod".

I'm pretty sure these are never reached, since NOT_EQUAL is always
converted into EQUAL in mp_binary_op.  No one should call
type.binary_op directly, they should always go through mp_binary_op
(or mp_obj_is_equal).

Pairs are limited to tuples so far.

Only calcsize() and unpack() functions provided so far, for little-endian
byte order. Format strings don't support repition spec (like "2b3i").

Unfortunately, dealing with all the various binary type sizes and alignments
will lead to quite a bloated "binary" helper functions  - if optimizing for
speed. Need to think if using dynamic parametrized algos makes more sense.

Needed to reinstate 2 delete opcodes, to specifically check that a local
is not deleted twice.

These two are apprerently the most concise and efficient way to convert
int to/from bytes in Python. The alternatives are struct and array modules,
but methods using them are more verbose in Python code and less efficient
in memory/cycles.

This makes the runtime and object APIs more consistent.  mp_store_subscr
functionality now moved into objects (ie list and dict store_item).