POP_BLOCK and POP_EXCEPT are now the same, and are always followed by a
JUMP.  So this optimisation reduces code size, and RAM usage of bytecode by
two bytes for each try-except handler.

After the previous commit it is no longer needed.

This patch fixes a bug in the VM when breaking within a try-finally.  The
bug has to do with executing a break within the finally block of a
try-finally statement.  For example:

    def f():
        for x in (1,):
            print('a', x)
            try:
                raise Exception
            finally:
                print(1)
                break
            print('b', x)
    f()

Currently in uPy the above code will print:

    a 1
    1
    1
    segmentation fault (core dumped)  micropython

Not only is there a seg fault, but the "1" in the finally block is printed
twice.  This is because when the VM executes a finally block it doesn't
really know if that block was executed due to a fall-through of the try (no
exception raised), or because an exception is active.  In particular, for
nested finallys the VM has no idea which of the nested ones have active
exceptions and which are just fall-throughs.  So when a break (or continue)
is executed it tries to unwind all of the finallys, when in fact only some
may be active.

It's questionable whether break (or return or continue) should be allowed
within a finally block, because they implicitly swallow any active
exception, but nevertheless it's allowed by CPython (although almost never
used in the standard library).  And uPy should at least not crash in such a
case.

The solution here relies on the fact that exception and finally handlers
always appear in the bytecode after the try body.

Note: there was a similar bug with a return in a finally block, but that
was previously fixed in b7352084

From https://github.com/micropython/oofatfs, branch work-R0.13c,
commit cb05c9486d3b48ffd6bd7542d8dbbab4b1caf790.

Large code pages (932, 936, 949, 950) have been removed from ffunicode.c
because they were not included in previous versions here.

To use HSI instead of HSE define MICROPY_HW_CLK_USE_HSI as 1 in the board
configuration file.  The default is to use HSE.

HSI has been made the default for the NUCLEO_F401RE board to serve as an
example, and because early revisions of this board need a hardware
modification to get HSE working.

Also, to make it possible for ports to provide their own lwipopts.h, the
default include directory of extmod/lwip-include is no longer added and
instead a port should now make sure the correct include directory is
included in the list (can still use extmod/lwip-include).

This demonstrates how to use external QSPI flash in XIP (execute in place)
mode.  The default configuration has all extmod/ code placed into external
QSPI flash, but other code can easily be put there by modifying the custom
f769_qspi.ld script.

A board can now use the make variables TEXT0_SECTIONS and TEXT1_SECTIONS to
specify the linker sections that should go in its firmware.  Defaults are
provided which give the existing behaviour.

This makes the QSPI more robust, in particular the timeout counter should
not be used with memory mapped mode (see F7 errata).

This port would rather keep the code size as RAM.

This optimisation eliminates the need to create a temporary normal dict.
The optimisation is enabled via MICROPY_COMP_CONST_LITERAL which is enabled
by default (although only has an effect if OrderdDict is enabled).

Thanks to @pfalcon for the initial idea and implementation.

Because "waiti 0" may have waited for a while (eg 500ms) and the internal
WDT may need to be fed immediately.

Fixes issue #4459.

Fixes issue #4499.

All exceptions that unwind through the async-with must be caught and
BaseException is the top-level class, which includes Exception and others.

Fixes issue #4552.

Some users of this module may require the LwIP stack to run at an elevated
priority, to protect against concurrency issues with processing done by the
underlying network interface.  Since LwIP doesn't provide such protection
it must be done here (the other option is to run LwIP in a separate thread,
and use thread protection mechanisms, but that is a more heavyweight
solution).

This is only correct for the extmod/uos_dupterm.c implementation however,
as e.g cc3200 implementation does the mp_load_method() itself, and anyway
requires `read` instead of `readinto`.

esp_wifi_connect will return ESP_OK for the normal path of execution which
just means the reconnect is started, not that it is actually reconnected.
In such a case wifi.isconnected() should return False until the
reconnection is complete.  After reconnect a GOT_IP event is called and it
will change wifi_sta_connected back to True.

A value of None for this argument is already supported, so the argument can
be made optional.

This optional parameter for network.LAN clock_mode can be used for cases
where the clock source is different from the default GPIO0.  Fixes #4502.