Multiplication of a tuple, list, str or bytes now yields an empty
sequence (instead of crashing).  Addresses issue #799

Also added ability to mult bytes on LHS by integer.

The only change is line-ending convesion to LF.

Also disable gc module on bare-arm port.

Also fixes compiler error in moductypes when compiled without debugging.

Addresses issue #778.

Can now index ranges with integers and slices, and reverse ranges
(although reversing is not very efficient).

Not sure how useful this stuff is, but gets us closer to having all of
Python's builtins.

reversed function now implemented, and works for tuple, list, str, bytes
and user objects with __len__ and __getitem__.

Renamed mp_builtin_len to mp_obj_len to make it publically available (eg
for reversed).

Saves code bytes and makes it faster, so why not?

Fixes #795.

Thanks to David Siorpaes.

Similar to other methods and following CPython3 strictness.

This happens for example for zero-size arrays. As .get_buffer() method now
has explicit return value, it's enough to distinguish success vs failure
of getting buffer.

Addresses some issues from #585.

Trying to move towards consistency, let's use _ exclusively in names of
source files (eg .c, .h, .csv).

This was a nasty bug to track down.  It only had consequences when the
heap size was just the right size to expose the rounding error in the
calculation of the finaliser table size.  And, a script had to allocate
a small (1 or 2 cell) object at the very end of the heap.  And, this
object must not have a finaliser.  And, the initial state of the heap
must have been all bits set to 1.  All these conspire on the pyboard,
but only if your run the script fresh (so unused memory is all 1's),
and if your script allocates a lot of small objects (eg 2-char strings
that are not interned).

Converts generted pins to use qstrs instead of string pointers.

This patch also adds the following functions:
pyb.Pin.names()
pyb.Pin.af_list()
pyb.Pin.gpio()

dir(pyb.Pin.board) and dir(pyb.Pin.cpu) also produce useful results.

pyb.Pin now takes kw args.

pyb.Pin.__str__ now prints more useful information about the pin
configuration.

I found the following functions in my boot.py to be useful:
```python
def pins():
    for pin_name in dir(pyb.Pin.board):
        pin = pyb.Pin(pin_name)
        print('{:10s} {:s}'.format(pin_name, str(pin)))

def af():
    for pin_name in dir(pyb.Pin.board):
        pin = pyb.Pin(pin_name)
        print('{:10s} {:s}'.format(pin_name, str(pin.af_list())))
```