Use computed goto instead of switching op-codes.

Fix parallel build.

Packets of 64 bytes length are not send to the host until the following
packet is sent.  Fixed by never sending packets of 64 bytes length.

The logic appears to be that (at least beginning of) sys.versions is the
version of reference Python language implemented, not version of particular
implementation.

Also, bump set versions at 3.4.0, based on @dpgeorge preference.

Similar to tuples, lists, dicts. Statically allocated strings don't have hash
computed.

This feature was proposed with initial hashing RFC, and is prerequisite for
seamless static str object definition.

Available via sys.std{in,out,err}.  Basic reading and writing supported.
Even sys.stdin.readline!

Enabled by MICROPY_ENABLE_PROPERTY.

Should address issue #475.

py: don't look for any additional headers when lexerunix is disabled

py: the entire `<unistd.h>` shouldn't be needed

Convert sys module to static allocation

objlist: Make .extend accept arbitrary iterable.

Must use mp_obj_get_type to get the type of an object.  Can't assume
mp_obj_t is castable to mp_obj_base_t.

Should fix issue #463.