MP_ALLOC_* -> MICROPY_ALLOC_*
MICROPY_PATH_MAX -> MICROPY_ALLOC_PATH_MAX
MICROPY_ENABLE_REPL_HELPERS -> MICROPY_HELPER_REPL
MICROPY_ENABLE_LEXER_UNIX -> MICROPY_HELPER_LEXER_UNIX
MICROPY_EXTRA_* -> MICROPY_PORT_*

See issue #35.

Parser shouldn't raise exceptions, so needs to check when memory
allocation fails.  This patch does that for the initial set up of the
parser state.

Also, we now put the parser object on the stack.  It's small enough to
go there instead of on the heap.

This partially addresses issue #558.

Draft approach towards resolving https://github.com/micropython/micropython/issues/560#issuecomment-42213955

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.

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.

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/.

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.

Remove unnecessary includes. Add includes that improve portability.

Implement not, shl and shr in mpz library.  Add function to create mpzs
on the stack, used for memory efficiency when rhs is a small int.
Factor out code to parse base-prefix of number into a dedicated function.

Based on suggestion by @dpgeorge at
https://github.com/micropython/micropython/pull/313

Specifically, VM's small ints are 31 bit, while parser's only 28. There's already
MP_OBJ_FITS_SMALL_INT(), so, for clarity, rename MP_FIT_SMALL_INT() to
MP_PARSE_FITS_SMALL_INT().

Each built-in exception is now a type, with base type BaseException.
C exceptions are created by passing a pointer to the exception type to
make an instance of.  When raising an exception from the VM, an
instance is created automatically if an exception type is raised (as
opposed to an exception instance).

Exception matching (RT_BINARY_OP_EXCEPTION_MATCH) is now proper.

Handling of parse error changed to match new exceptions.

mp_const_type renamed to mp_type_type for consistency.

LOAD_METHOD bug was: emitbc did not correctly calculate the amount of
stack usage for a LOAD_METHOD operation.

small int bug was: int was being used to pass small ints, when it should
have been machine_int_t.

TODO: Check lexer/parse/compile error path for leaks too.

Can now have null bytes in strings.  Can define ROM qstrs per port using
qstrdefsport.h

Exceptions know source file, line and block name.

Also tidy up some debug printing functions and provide a global
flag to enable/disable them.

Byte code has a map from byte-code offset to source-code line number,
used to give better error messages.

Parser no longer prints an error, but instead returns an exception ID
and message.

Long int is something which doesn't fit into SMALL_INT partion of
machine_int_t. But it's also something which doesn't fit into
machine_int_t in the first place.

A big change.  Micro Python objects are allocated as individual structs
with the first element being a pointer to the type information (which
is itself an object).  This scheme follows CPython.  Much more flexible,
not necessarily slower, uses same heap memory, and can allocate objects
statically.

Also change name prefix, from py_ to mp_ (mp for Micro Python).