Those trace messages have never proven to be useful and they make
the code 9K bigger.

Use the simplelink wrappers instead. This is one step further
towards having a single module for the cc3200 and the cc3100.

The implementation of these functions is very large (order 4k) and they
are rarely used, so we don't enable them by default.

They are however enabled in stmhal and unix, since we have the room.

Also includes documentation about minimum baudrate.

Addresses issue #1090.

This commit will not build, it exists just to track changes.

Preparing this to move to drivers/ directory, want to make it as similar
to original code from TI as possible.

This is how it should be, so one knows exactly where the includes are
coming from.

Saves around 1.3K. At the same time re-enable MICROPY_PY_SYS_EXIT
since it doesn't take much space and might be useful for certain
scripts.

Issue #1122 should now be fixed.

Disabling MICROPY_EMIT_INLINE_THUMB gives us back around 6K of
precious RAM.

I2C objects can be freed by the GC and a __del__ method is provided
in order to de-init the peripheral prior to being garbage collected.
UART objects are now added to a local list and this list is now part
of the VM_STATE.

Most of printing infrastructure now uses streams, but mp_obj_print() used
libc's printf(), which led to weird buffering issues in output. So, switch
mp_obj_print() to streams too, even though it may make sense to move it to
a separate file, as it is purely a debugging function now.