This removes hard-coded DMA init params from dma_init(), instead defining
these parameters in a DMA_InitTypeDef struct that gets passed as an
argument to dma_init()
This makes dma_init more generic so it can be used for I2S and SD Card,
which require different initialization parameters.

To make it the same as SPI and UART.

Previous to this patch the printing mechanism was a bit of a tangled
mess.  This patch attempts to consolidate printing into one interface.

All (non-debug) printing now uses the mp_print* family of functions,
mainly mp_printf.  All these functions take an mp_print_t structure as
their first argument, and this structure defines the printing backend
through the "print_strn" function of said structure.

Printing from the uPy core can reach the platform-defined print code via
two paths: either through mp_sys_stdout_obj (defined pert port) in
conjunction with mp_stream_write; or through the mp_plat_print structure
which uses the MP_PLAT_PRINT_STRN macro to define how string are printed
on the platform.  The former is only used when MICROPY_PY_IO is defined.

With this new scheme printing is generally more efficient (less layers
to go through, less arguments to pass), and, given an mp_print_t*
structure, one can call mp_print_str for efficiency instead of
mp_printf("%s", ...).  Code size is also reduced by around 200 bytes on
Thumb2 archs.

With this patch str/bytes construction is streamlined.  Always use a
vstr to build a str/bytes object.  If the size is known beforehand then
use vstr_init_len to allocate only required memory.  Otherwise use
vstr_init and the vstr will grow as needed.  Then use
mp_obj_new_str_from_vstr to create a str/bytes object using the vstr
memory.

Saves code ROM: 68 bytes on stmhal, 108 bytes on bare-arm, and 336 bytes
on unix x64.

Addresses issue #921.

Addressing issue #50, still some way to go yet.

to maintain compatibility with existing code.

to allow these methods to transmit 16 bit addresses to an i2c device
Add 'memaddr_use_16b' to qstrdefsport.h

See discussion in issue #50.

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/.

Decided to write own script to pull documentation from comments in C code.
Style for writing auto generated documentation is: start line with ///
and then use standard markdown to write the comment.  Keywords
recognised by the scraper begin with backslash.  See code for examples.

Running: python gendoc.py modpyb.c accel.c adc.c dac.c extint.c i2c.c
led.c pin.c rng.c servo.c spi.c uart.c usrsw.c, will generate a HTML
structure in gendoc-out/.

gendoc.py is crude but functional.  Needed something quick, and this was
it.

The HAL handles for the I2C/SPI objects are rather large, so we don't
want to unnecessarily include them.

Also some updates to compile with latest changes to core py.

Main reason for expanding buffer protocol API was to support writes to a
buffer in ADC module (see read_timed).  With this change you can now
create an array of arbitrary type and ADC.read_timed will store into
that array in the correct format (byte, int, float).  I wonder though if
all these changes were really worth it to support just this function.
Hopefully this enhanced buffer protocol API (with typecode specified)
will be used elsewhere.

Simple way to find the address of an attached I2C device.

Must use mp_obj_get_type to get the type of an object.  Can't assume
mp_obj_t is castable to mp_obj_base_t.

This does not affect code size or performance when debugging turned off.

To address issue #420.

Pretty much everyone needs to include map.h, since it's such an integral
part of the Micro Python object implementation.  Thus, the definitions
are now in obj.h instead.  map.h is removed.

Mostly just a global search and replace.  Except rt_is_true which
becomes mp_obj_is_true.

Still would like to tidy up some of the names, but this will do for now.