Warnings lead to programming errors - as expected.

splitlines() occurs ~179 times in CPython3 standard library, so was
deemed worthy to implement. The method has subtle semantic differences
from just .split("\n"). It is also defined as working for any end-of-line
combination, but this is currently not implemented - it works only with
LF line-endings (which should be OK for text strings on any platforms,
but not OK for bytes).

Currently supports only x64 and Thumb2 archs.

This implementation is smaller (in code size) than #1024.

Reference MCU is dsPIC33J256GP506 with 256k ROM and 8k RAM, on the dsPIC
DSC Starter Kit board.  The REPL works, GC works, pyb module has LED and
Switch objects.  It passes some tests from the test suite (most it can't
run because it doesn't have the Python features enabled).

Also rename call_args_t to mp_call_args_t.

I.e. in this mode, C stack will never be used to call a Python function,
but if there's no free heap for a call, it will be reported as
RuntimeError (as expected), not MemoryError.

Allow for reuse for stackless design, where preparing args is separate from
calling.

Current version has been numbered as 0.9.0 since Timers/PWM support
is still missing.

Error reporting is also changed from detailed to terse, as with the
rest of the CC3200's modules. All this combined saves ~200 bytes.

Conditional on MICROPY_PY_ALL_SPECIAL_METHODS.

Per https://docs.python.org/3/library/functions.html#round, 2-args format
guaranteedly returns float.

Add example: using named function for the Timer's callback.
Add note: improving traceback inside interrupt timers.

There are lots of cosmetic changes, but this release brings a  very
important bug fix:
 - Fixed f_unlink() does not remove cluster chain of the file.

With R0.10c if you try to write a file that is too large to fit in the
free space of the drive, the operation fails, you delete the incomplete
file, and it seems to be erased, but the space is not really freed,
because any subsequent write operations fail because the drive is
"still" full. The only way to recover from this is by formatting the
drive. I can confirm that R0.11 fixes the problem.

Disabled by default.  Enabled on unix and windows ports.

Setting the word count before a SPI transaction is only needed when
using DMA.

Increasing it from 1K to 2K gives more freedom to the callback
handlers, before this, simply nesting a function call into a
printf would cause a stack overflow.