Pairs are limited to tuples so far.

A specific target can define either MP_ENDIANNESS_LITTLE or MP_ENDIANNESS_BIG
to 1. Default is MP_ENDIANNESS_LITTLE.

TODO: Autodetect based on compiler predefined macros?

Update .gitignore

Tweak pybcdc.inf to match recent changes to pybcdc.h

Also contains raw memory read/write functions, read8, read16, read32,
write8, write16, write32.  Can now do:

stm.write16(stm.GPIOA + stm.GPIO_BSRRL, 1 << 13)

This turns on the red LED.

With the new constant folding, the above constants for the GPIO address
are actually compiled to constants (and the addition done) at compile
time.  For viper code and inline assembler, this optimisation will make
a big difference.  In the inline assembler, using these constants would
not be possible without this constant folding.

Working towards trying to support compile-time constants (see discussion
in issue #227), this patch allows the compiler to look inside arbitrary
uPy objects at compile time.  The objects to search are given by the
macro MICROPY_EXTRA_CONSTANTS (so they must be constant/ROM objects),
and the constant folding occures on forms base.attr (both base and attr
must be id's).

It works, but it breaks strict CPython compatibility, since the lookup
will succeed even without importing the namespace.

Add test failure logs

Can do this now that the stack size calculation is improved.

Much less of a hack now.  Hopefully it's correct!

Previously, a failed malloc/realloc would throw an exception, which was
not caught.  I think it's better to keep the parser free from NLR
(exception throwing), hence this patch.

Now reads in small chunks at a time.

Labels should never be negative, and this modified type signature
reflects that.

Eg, in CPython stdlib, email/header.py has a form-feed character.

Only calcsize() and unpack() functions provided so far, for little-endian
byte order. Format strings don't support repition spec (like "2b3i").

Unfortunately, dealing with all the various binary type sizes and alignments
will lead to quite a bloated "binary" helper functions  - if optimizing for
speed. Need to think if using dynamic parametrized algos makes more sense.

Syntax is usual C #if*/#endif, but each qstr must be wrapped individually.