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.

Now reads in small chunks at a time.

Labels should never be negative, and this modified type signature
reflects that.

Eg, in CPython stdlib, email/header.py has a form-feed character.

Only calcsize() and unpack() functions provided so far, for little-endian
byte order. Format strings don't support repition spec (like "2b3i").

Unfortunately, dealing with all the various binary type sizes and alignments
will lead to quite a bloated "binary" helper functions  - if optimizing for
speed. Need to think if using dynamic parametrized algos makes more sense.

Syntax is usual C #if*/#endif, but each qstr must be wrapped individually.

Remove exception name from inside the exception message

This prevents micropython printing exception messages like
ImportError: ImportError: No module named 'foo'

mp_obj_is_integer should be used to check if an object is of integral
type.  It returns true for bool, small int and long int.

Needed to reinstate 2 delete opcodes, to specifically check that a local
is not deleted twice.

So we can add more flags.

Small reduction in ROM, heap and stack usage.

Convert int types to uint where sensible, and then to uint8_t or
uint16_t where possible to reduce RAM usage.

Can now calibrate, set pulse width, angle and speed.

Fix make-pins.py to support having multiple names for a pin.