Without this patch deleting a property, or class with descriptor, will
call the setter with a NULL value and lead to a crash.

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.