Use CTRL-E to enter paste mode.  Prompt starts with "===" and accepts
all characters verbatim, echoing them back.  Only control characters are
CTRL-C which cancels the input and returns to normal REPL, and CTRL-D
which ends the input and executes it.  The input is executed as though
it were a file.  The input is not added to the prompt history.

With this patch parse nodes are allocated sequentially in chunks.  This
reduces fragmentation of the heap and prevents waste at the end of
individually allocated parse nodes.

Saves roughly 20% of RAM during parse stage.

Follow the same format as other ports using the macro to include
the HAL header.

See issue #1306.

Using MICROPY_PY_SYS_PATH_DEFAULT macro define. A usecase is building a
distribution package, which should not have user home path by default in
sys.path. In such case, MICROPY_PY_SYS_PATH_DEFAULT can be defined on
make command-line (using CFLAGS_EXTRA).

This gets uPy readline working with unix port, with tab completion and
history.  GNU readline is still supported, configure using
MICROPY_USE_READLINE variable.

This allows the output of the extra-coverage tests to be checked using
the normal run-tests script.

The function and corresponding command-line option are only enabled for
the coverage build.  They are used to exercise uPy features that can't
be properly tested by Python scripts.

Also rename py-version.h to mpversion.h for consistency with mpconfig.h.

Previous to this patch the printing mechanism was a bit of a tangled
mess.  This patch attempts to consolidate printing into one interface.

All (non-debug) printing now uses the mp_print* family of functions,
mainly mp_printf.  All these functions take an mp_print_t structure as
their first argument, and this structure defines the printing backend
through the "print_strn" function of said structure.

Printing from the uPy core can reach the platform-defined print code via
two paths: either through mp_sys_stdout_obj (defined pert port) in
conjunction with mp_stream_write; or through the mp_plat_print structure
which uses the MP_PLAT_PRINT_STRN macro to define how string are printed
on the platform.  The former is only used when MICROPY_PY_IO is defined.

With this new scheme printing is generally more efficient (less layers
to go through, less arguments to pass), and, given an mp_print_t*
structure, one can call mp_print_str for efficiency instead of
mp_printf("%s", ...).  Code size is also reduced by around 200 bytes on
Thumb2 archs.

Without that, "import http.client" failed due to max recursion.

To enable parsing constants more efficiently, mp_parse should be allowed
to raise an exception, and mp_compile can already raise a MemoryError.
So these functions need to be protected by an nlr push/pop block.

This patch adds that feature in all places.  This allows to simplify how
mp_parse and mp_compile are called: they now raise an exception if they
have an error and so explicit checking is not needed anymore.

See issue #699.

See issue #699.

This patch consolidates all global variables in py/ core into one place,
in a global structure.  Root pointers are all located together to make
GC tracing easier and more efficient.

This fixes FORCED_EXIT internal flag leaking into Windows exit code.

The function is modeled after traceback.print_exception(), but unbloated,
and put into existing module to save overhead on adding another module.
Compliant traceback.print_exception() is intended to be implemented in
micropython-lib in terms of sys.print_exception().

This change required refactoring mp_obj_print_exception() to take pfenv_t
interface arguments.

Addresses #751.

mp_lexer_t type is exposed, mp_token_t type is removed, and simple lexer
functions (like checking current token kind) are now inlined.

This saves 784 bytes ROM on 32-bit unix, 348 bytes on stmhal, and 460
bytes on bare-arm.  It also saves a tiny bit of RAM since mp_lexer_t
is a bit smaller.  Also will run a bit more efficiently.

TODO: Merge useful functionality from modpyb too.

The specifier should go after the number, before size suffix like 'k' or 'm'.
E.g.: "-X heapsize=100wk" will use 100K heap on 32-bit system and 200K - on
64-bit.

Also, move bytecode dumps to -v -v, because they're too verbose for just -v.

Support for packages as argument not implemented, but otherwise error and
exit handling should be correct. This for example will allow to do:

pip-micropython install micropython-test.pystone
micropython -m test.pystone

This allows to implement KeyboardInterrupt on unix, and a much safer
ctrl-C in stmhal port.  First ctrl-C is a soft one, with hope that VM
will notice it; second ctrl-C is a hard one that kills anything (for
both unix and stmhal).

One needs to check for a pending exception in the VM only for jump
opcodes.  Others can't produce an infinite loop (infinite recursion is
caught by stack check).

For kilobytes and megabytes respectively.

In unix port, mem_info(1) now prints pretty GC alloc table.

Addresses issue #915.

Per new conventions, we'd like to consistently use "u*" naming conventions
for modules which don't offer complete CPython compatibility, while offer
subset or similar API.

This should pretty much resolve issue #50.