Before this patch, (x+y)*z would be parsed to a tree that contained a
redundant identity parse node corresponding to the parenthesis.  With
this patch such nodes are optimised away, which reduces memory
requirements for expressions with parenthesis, and simplifies the
compiler because it doesn't need to handle this identity case.

A parenthesis parse node is still needed for tuples.

Handles, eg, "{:>20}".format("foo"), where there is no explicit spec for
the type of the argument.

Note that even though wrapped in MICROPY_CPYTHON_COMPAT, it is not
fully compatible because the modifications to the dictionary do not
propagate to the actual instance members.

Only types whose iterator instances still fit in 4 machine words have
been changed to use the polymorphic iterator.

Reduces Thumb2 arch code size by 264 bytes.

The traceback array stores qstrs and line numbers.  qstrs are typed as
size_t, and line numbers should safely fit in size_t as well.

To comply with already established scheme for extmod's.

That's just function which sets/gets dup terminal object, and can be
easily reused across ports.

To allow simple zero-terminated lexers.

It's possible to have a fixed map that is properly hashed (ie not
simply ordered).

Otherwise build fails if uctypes is disabled.

Previously, mark operation weren't logged at all, while it's quite useful
to see cascade of marks in case of over-marking (and in other cases too).
Previously, sweep was logged for each block of object in memory, but that
doesn't make much sense and just lead to longer output, harder to parse
by a human. Instead, log sweep only once per object. This is similar to
other memory manager operations, e.g. an object is allocated, then freed.
Or object is allocated, then marked, otherwise swept (one log entry per
operation, with the same memory address in each case).

Map indicies are most commonly a qstr, and adding a fast-path for hashing
of a qstr increases overall performance of the runtime.

On pyboard there is a 4% improvement in the pystone benchmark for a cost
of 20 bytes of code size.  It's about a 2% improvement on unix.

When looking up and extracting an attribute of an instance, some
attributes must bind self as the first argument to make a working method
call.  Previously to this patch, any attribute that was callable had self
bound as the first argument.  But Python specs require the check to be
more restrictive, and only functions, closures and generators should have
self bound as the first argument

Addresses issue #1675.

Addresses issue #1636.

POSIX doesn't guarantee something like that to work, but it works on any
system with careful signal implementation. Roughly, the requirement is
that signal handler is executed in the context of the process, its main
thread, etc. This is true for Linux. Also tested to work without issues
on MacOSX.

I.e. the expected result for above is b"foo", whereas previously we got
b"b'foo'".

This makes all tests pass again for 64bit windows builds which would
previously fail for anything printing ranges (builtin_range/unpack1)
because they were printed as range( ld, ld ).

This is done by reusing the mp_vprintf implementation for MICROPY_OBJ_REPR_D
for 64bit windows builds (both msvc and mingw-w64) since the format specifier
used for 64bit integers is also %lld, or %llu for the unsigned version.

Note these specifiers used to be fetched from inttypes.h, which is the
C99 way of working with printf/scanf in a portable way, but mingw-w64
wants to be backwards compatible with older MS C runtimes and uses
the non-portable %I64i instead of %lld in inttypes.h, so remove the use
of said header again in mpconfig.h and define the specifiers manually.

Ideally we'd use %zu for size_t args, but that's unlikely to be supported
by all runtimes, and we would then need to implement it in mp_printf.
So simplest and most portable option is to use %u and cast the argument
to uint(=unsigned int).

Note: reason for the change is that UINT_FMT can be %llu (size suitable
for mp_uint_t) which is wider than size_t and prints incorrect results.

MICROPY_ENABLE_COMPILER can be used to enable/disable the entire compiler,
which is useful when only loading of pre-compiled bytecode is supported.
It is enabled by default.

MICROPY_PY_BUILTINS_EVAL_EXEC controls support of eval and exec builtin
functions.  By default they are only included if MICROPY_ENABLE_COMPILER
is enabled.

Disabling both options saves about 40k of code size on 32-bit x86.

Saves 88 bytes on Thumb2, and 200 bytes on x86-64 archs.

To let unix port implement "machine" functionality on Python level, and
keep consistent naming in other ports (baremetal ports will use magic
module "symlinking" to still load it on "import machine").

Fixes #1701.

For builds where mp_uint_t is larger than size_t, it doesn't make
sense to use such a wide type for qstrs.  There can only be as many
qstrs as there is address space on the machine, so size_t is the correct
type to use.

Saves about 3000 bytes of code size when building unix/ port with
MICROPY_OBJ_REPR_D.

Only enabled for MICROPY_OBJ_REPR_D.

size_t is the correct type to use to count things related to the size of
the address space.  Using size_t (instead of mp_uint_t) is important for
the efficiency of ports that configure mp_uint_t to larger than the
machine word size.