This patch consolidates the Python logic for division/modulo to one place
within the bignum code.

When DIG_SIZE=32, a uint32_t is used to store limbs, and no normalisation
is needed because the MSB is already set, then there will be left and
right shifts (in C) by 32 of a 32-bit variable, leading to undefined
behaviour.  This patch fixes this bug.

Also do that only for the first word in a line. The idea is that when you
start up interpreter, high chance that you want to do an import. With this
patch, this can be achieved with "i<tab>".

Starts WebREPL server in foreground and waits for (single) connection.

Initialisation of CAN objects should now behave as other peripheral
objects.

Fixes issue #2001.

This will launch about as many compiler instances as there are logical
processors on a machine, and as such significantly speeds up compilation.

The socket should either connect to `addr` or `addr_info[0][-1]`. Not to `addr[0][-1]`.

They fail on builds with 32-bit word size.

The type is an unsigned 8-bit value, since bytes objects are exactly
that.  And it's also sensible for unicode strings to return unsigned
values when accessed in a byte-wise manner (CPython does not allow this).

This commit fixes issue #2045

It interferes with running testsuite. master branch should be optimized for
development, so any features which interfere with that, would need to be
disabled by default.

To get consistent error messages, etc.

Addresses issue #2034.

This constant is no longer part of hardware API (replaced with just None),
and is a default, so not needed in calls.

Also raise an exception for machine.freq and machine.deepsleep on this
MCU, since they are not yet implemented.

The main thing is to change the DMA code in a way that the structure
DMA_Stream_TypeDef (which is similar to DMA_Channel_TypeDef on stm32l4)
is no longer used outside of dma.c, as this structure only exists for the
F4 series.  Therefore I introduced a new structure (dma_descr_t) which
handles all DMA specific stuff for configuration.  Further the periphery
(spi, i2c, sdcard, dac) does not need to know the internals of the dma.

At http://micropython.org/webrepl .

.time() returns seconds since MicroPython epoch (2000-01-01 00:00UTC),
.settime() sends current system time, assuming UTC timezone.