This patch simplifies the glue between native emitter and runtime,
and handles viper code like inline assember: return values are
converted to Python objects.

Fixes issue #531.

bytecode is the more widely used.  See issue #590.

Should support everything supported by strings.

So one has some chance to convert numeric op code into symbol.

You can now do:

    X = const(123)
    Y = const(456 + X)

and the compiler will replace X and Y with their values.

See discussion in issue #266 and issue #573.

Extend the windows port so it compiles with the toolchain from Visual Studio 2013

Just a start, no working code yet.  As per issue #573.

Enable only on unix. To avoid unpleasant surprises with error codes.

In case of empty non-blocking read()/write(), both return None. read()
cannot return 0, as that means EOF, so returns another value, and then
write() just follows. This is still pretty unexpected, and typical
"if not len:" check would treat this as EOF. Well, non-blocking files
require special handling!

This also kind of makes it depending on POSIX, but well, anything else
should emulate POSIX anyway ;-).

Doesn't help with RAM reduction because doc strings are interned as soon
as they are encountered, which is too soon to do any optimisations on
them.

Need to have a policy as to how far we go adding keyword support to
built ins.  It's nice to have, and gets better CPython compatibility,
but hurts the micro nature of uPy.

Addresses issue #577.

Addresses #567.

Addresses #577.

...to some compilers who can't process 2 zero-sized arrays in structs. It's
never referenced directly anyway.

See disussion on #568 as well.

There are 2 locations in parser, and 1 in compiler, where memory
allocation is not precise.  In the parser it's the rule stack and result
stack, in the compiler it's the array for the identifiers in the current
scope.  All other mallocs are exact (ie they don't allocate more than is
needed).

This patch adds tuning options (MP_ALLOC_*) to mpconfig.h for these 3
inexact allocations.

The inexact allocations in the parser should actually be close to
logarithmic: you need an exponentially larger script (absent pathological
cases) to use up more room on the rule and result stacks.  As such, the
default allocation policy for these is now to start with a modest sized
stack, but grow only in small increments.

For the identifier arrays in the compiler, these now start out quite
small (4 entries, since most functions don't have that many ids), and
grow incrementally by 6 (since if you have more ids than 4, you probably
have quite a few more, but it wouldn't be exponentially more).

Partially addresses issue #560.

This will work if MICROPY_DEBUG_PRINTERS is defined, which is only for
unix/windows ports. This makes it convenient to user uPy normally, but
easily get bytecode dump on the spot if needed, without constant recompiles
back and forth.

TODO: Add more useful debug output, adjust verbosity level on which
specifically bytecode dump happens.

Blanket wide to all .c and .h files.  Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.

Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.

By default mingw outputs 3 digits instead of the standard 2 so all float
tests using printf fail. Using setenv at the start of the program fixes this.
To accomodate calling platform specific initialization a
MICROPY_MAIN_INIT_FUNC macro is used which is called in mp_init()

This follows up 0a7e01ae.

Well, it is bound to "detailed error reporting", but that's closest what we
have now without creating new entities.

The original parsing would error out on any C declarations that are not typedefs
or extern variables. This limits what can go in mpconfig.h and mpconfigport.h,
as they are included in qstr.h. For instance even a function declaration would be
rejected and including system headers is a complete no-go.
That seems too limiting for a global config header, so makeqstrdata now
ignores everything that does not match a qstr definition.

alloca() is declared in alloca.h which als happens to be included by stdlib.h.
On mingw however it resides in malloc.h only.
So if we include alloca.h directly, and add an alloca.h for mingw in it's port
directory we can get rid of the mingw-specific define to include malloc.h
and the other ports are happy as well.