Takes slice object and sequence length and computes subsequence indexes
for case of slice step=1.

IS_NOT and NOT_IN are now compiled to IS + NOT and IN + NOT, with a new
special NOT bytecode.

Still todo: break/continue from within the finally block itself.

TODO: Decide if we really need separate bytecode for creating functions
with default arguments - we would need same for closures, then there're
keywords arguments too. Having all combinations is a small exponential
explosion, likely we need just 2 cases - simplest (no defaults, no kw),
and full - defaults & kw.

This properly implements return from try/finally block(s).

TODO: Consider if we need to do any value stack unwinding for RETURN_VALUE
case. Intuitively, this is "success" return, so value stack should be in
good shape, and unwinding shouldn't be required.

rt_call_function_n_kw did check for integers but not for strings
being called. Added a check so running "a"() won't SIGSEV but
throw an exception.

Also, handle SETUP_FINALLY opcode.

Allows to have nested try blocks with except filters.

TODO: Don't add END_FINALLY's exception re-raise points to traceback.

__bool__() and __len__() are just the same as __neg__() or __invert__(),
and require efficient dispatching implementation (not requiring search/lookup).
type->unary_op() is just the right choice for this short of adding
standalone virtual method(s) to already big mp_obj_type_t structure.

To alloc complete memory alloc flow tracing.

We still have FAST_[0,1,2] byte codes, but they now just access the
fastn array (before they had special local variables).  It's now
simpler, a bit faster, and uses a bit less stack space (on STM at least,
which is most important).

The only reason now to keep FAST_[0,1,2] byte codes is for compressed
byte code size.

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.

This is special feature for FFI.

Fixed '#ifdef's so Linux would compile again and added
.scl and .type for Windows.