Fixes issue #2176.

It's useful to be able to use symbolic links to add files and directories
to the set of scripts to be frozen.

This new config option allows to control whether MicroPython uses its own
internal printf or not (if not, an external one should be linked in).
Accompanying this new option is the inclusion of lib/utils/printf.c in the
core list of source files, so that ports no longer need to include it
themselves.

Adds horizontal scrolling. Right now, I'm just leaving the margins
created by the scrolling as they were -- so they will repeat the
edge of the framebuf. This is fast, and the user can always fill
the margins themselves.

Consistency and formatting.

SPI(1) is not used for hardware SPI. Few more details are provided.

modpybhspi now does the needed multiplexing, calling out to modpybspi
(bitbanging SPI) for suitable peripheral ID's. modmachinespi (previous
multiplexer class) thus not needed and removed.

modpybhspi also updated to following standard SPI peripheral naming:
SPI0 is used for FlashROM and thus not supported so far. SPI1 is available
for users, and thus needs to be instantiated as:

spi = machine.SPI(1, ...)

There functionality is available via standard SPI class.

Both tested to work. (WDT_RESET can be seen by issuing machine.disable_irq()
and waiting for WDT reset, SOFT_RESET - by machine.reset()).

This set the CPU frequency to 216 MHz (the max) and
leaves the USB Frequency at 48 MHz.

These settings were copied from one of the HAL examples.

So that users of framebuf don't need to have stmhal directory in their
path.  (Eventually the font can be moved elsewhere.)

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>

Usage:

    import machine
    wdt = machine.WDT(0, 5000) # 5 second timeout
    wdt.feed()

Thanks to Moritz for the initial implementation.

There was a bug in `framebuf1_fill` function, that makes it leave a few
lines unfilled at the bottom if the height is not divisible by 8.

A similar bug is fixed in the scroll method.

This makes it more efficient at runtime to hash str/bytes objects.

Makes it easier to access them without passing around another dict of the
config values.

Arguments of an unknown type cannot be skipped and continuing to parse a
format string after encountering an unknown format specifier leads to
undefined behaviour.  This patch helps to find use of unsupported formats.

With backwards compatibility for pyboard.

The idea is that all ports can use these helper methods and only need to
provide initialisation of the SPI bus, as well as a single transfer
function.  The coding pattern follows the stream protocol and helper
methods.

This extra forward slash for the starting-point directory is unnecessary
and leads to additional slashes on Max OS X which mean that the frozen
files cannot be imported.

Fixes #2374.

Or alternatively, refer to an exact library file, not just phony target
"lib".