To allow access and testing without complex access methods like WiFi.
Enabled for both WiPy and TI LaunchXL.

UART REPL support was lost in os.dupterm() refactorings, etc. As
os.dupterm() is there, implement UART REPL support at the high level -
if MICROPY_STDIO_UART is set, make default boot.py contain os.dupterm()
call for a UART. This means that changing MICROPY_STDIO_UART value will
also require erasing flash on a module to force boot.py re-creation.

To make moduselect be usable by any port.

The constants MP_IOCTL_POLL_xxx, which were stmhal-specific, are moved
from stmhal/pybioctl.h (now deleted) to py/stream.h.  And they are renamed
to MP_STREAM_POLL_xxx to be consistent with other such constants.

All uses of these constants have been updated.

If a port defines MICROPY_READER_POSIX or MICROPY_READER_FATFS then
lexer.c now provides an implementation of mp_lexer_new_from_file using
the mp_reader_new_file function.

Implementations of persistent-code reader are provided for POSIX systems
and systems using FatFS.  Macros to use these are MICROPY_READER_POSIX and
MICROPY_READER_FATFS respectively.  If an alternative implementation is
needed then a port can define the function mp_reader_new_file.

Per the latest HW API, "SPI" class implements only master side of the
protocol, so mode=SPI.MASTER (which was static for WiPy anyway) is not
required (or allowed). This change is required to correspond to updated
documentation of machine.SPI class which no longer lists "mode".

Its addition was due to an early exploration on how to add CPython-like
stream interface. It's clear that it's not needed and just takes up
bytes in all ports.

In order to have more fine-grained control over how builtin functions are
constructed, the MP_DECLARE_CONST_FUN_OBJ macros are made more specific,
with suffix of _0, _1, _2, _3, _VAR, _VAR_BETEEN or _KW.  These names now
match the MP_DEFINE_CONST_FUN_OBJ macros.

Running Python code on a hard interrupt is incompatible with having a GIL,
because most of the time the GIL will be held by the user thread when the
interrupt arrives.  Hard interrupts mean that we should process them right
away and hence can't wait until the GIL is released.

The problem with the current code is that a hard interrupt will try to
exit/enter the GIL while it is still held by the user thread, hence leading
to a deadlock.

This patch works around such a problem by just making GIL exit/enter a
no-op when in an interrupt context, or when interrupts are disabled.

See issue #2406.

Adds 1072 bytes to the code size.

To conform with Hardware API.

Reduces code size by 632 bytes.

This resolves issue #2343.

One can instead lookup __name__ in the modules dict to get the value.

machine.POWER_ON is renamed to machine.PWRON_RESET to match other
reset-cause constants that all end in _RESET.  The cc3200 port keeps a
legacy definition of POWER_ON for backwards compatibility.

This new config option allows to control whether MicroPython uses its own
internal printf or not (if not, an external one should be linked in).
Accompanying this new option is the inclusion of lib/utils/printf.c in the
core list of source files, so that ports no longer need to include it
themselves.

This type was used only for the typedef of mp_obj_t, which is now defined
by the object representation.  So we can now remove this unused typedef,
to simplify the mpconfigport.h file.

These macros are broken and are anyway unused on these two ports.  If they
are ever needed in the future then their implementation can be taken from
either stmhal (working macros in mpconfigport.h) or esp8266 (functions).

Threading is not used in the bootloader but the config optios are still
enabled so we must exclude including FreeRTOS.h.

The 16k FreeRTOS heap originally had all TCBs and stacks dynamically
allocated within it (plus semaphores and some other things).  Now that
xTaskCreateStatic is used instead of xTaskCreate, the TCBs and stacks
are allocated statically and no longer use any of the FreeRTOS heap.
Therefore, the FreeRTOS stack can be shrunk by the amount that has been
made static.  Furthermore, the TCBs and stack that are now static should
be placed in the .rtos_heaps section of RAM because this RAM is treated
specially by the bootloader (the bootloader executes from the first 16k
of RAM and loads the firmware into the section starting after the 16k).

After this patch the FreeRTOS heap (ucHeap) is 7200 bytes.  The memory
available for the MicroPython heap is 54936 bytes (including GC overhead).

In VStartSimpleLinkSpawnTask we change xTaskCreate to xTaskCreateStatic
so that the task is created using statically allocated memory for the TCB
and stack.

This means that xTaskCreate function is no longer needed (the static
version is now used exclusively).

This function is no longer used.  Having the .boot section attribute
meant that it was included in the firmware regargless of use.  Without
this attribute the linker can remove the function.

This config variable is now needed regardless of whether threading is
enabled or not.

Otherwise there could be a deadlock, with the GC's mutex and
thread_mutex.

Reduced the need for the FreeRTOS heap to allocate the mutex.

This allows to statically allocate the TCB (thread control block) and
thread stack in the BSS segment, reducing the need for dynamic memory
allocation.

We rely on the port setting and adjusting the stack size so there is
enough room to recover from hitting the stack limit.

Can create a new thread and run it.  Does not use the GIL at this point.