Use uos.dupterm for REPL configuration of the main USB_VCP(0) stream on
dupterm slot 1, if USB is enabled.  This means dupterm can also be used to
disable the boot REPL port if desired, via uos.dupterm(None, 1).

For efficiency this adds a simple hook to the global uos.dupterm code to
work with streams that are known to be native streams.

Single core is still supported, just by adding CONFIG_FREERTOS_UNICORE=y to
a custom sdkconfig file.

Unnamed semaphores (via sem_init) are not supported on this OS.  See #4465.

These macros are unused, and they can conflict with other entities by the
same name.  If needed they can be provided as static inline functions, or
just functions.

Fixes issue #4559.

This allows formatting SD cards, larger flash etc which do not support the
default FAT16/SFD format mode.

If HSI is used the calibration value must be valid.  Fixes #4596.

This means the schedule operates on a first-in, first-executed manner
rather than the current last-in, first executed.

Adds support for hardware i2c to the zephyr port. Similar to other ports
such as stm32 and nrf, we only implement the i2c protocol functions
(readfrom and writeto) and defer memory operations (readfrom_mem,
readfrom_mem_into, and writeto_mem) to the software i2c implementation.
This may need to change in the future because zephyr is considering
deprecating its i2c_transfer function in favor of i2c_write_read; in this
case we would probably want to implement the memory operations directly
using i2c_write_read.

Tested with the accelerometer on frdm_k64f and bbc_microbit boards.

For gpio_hold_en() to work properly (not draw additional current) pull
up/down must be disabled when hold is enabled.  This patch makes sure this
is the case by reworking the pull constants to be a bit mask.

Adding section about on how to disable use of the linker flag
-flto, by setting the LTO=0 argument to Make. Also, added a
note on recommended toolchains to use that works well with
LTO enabled.

In 1808b2e8 it was replaced by MICROPY_VFS
and related code.

This allows boards that need USE_MBOOT to be built properly whether or not
USE_MBOOT=1 is specified when building mboot.

Removing linker script for nrf52840 s140 v6.0.0 as pca10056
target board now points to the new v6.1.1. Also, removing the
entry from the download_ble_stack.sh script.

This patch moves pca10056/nrf52840 target board to use
the new SoftDevice s140 v6.1.1 instead of the legacy v6.0.0.

Updating download script to fetch the new SoftDevice, and
adding corresponding linker script for the BLE stack.

Removing linker script for nrf52832 s132 v6.0.0 as all target
boards now points to the new v6.1.1. Also, removing the entry
from the download_ble_stack.sh script.

This patch moves all the nrf52832 target boards to use the
new SoftDevice s132 v6.1.1 instead of the legacy v6.0.0.

Updating download script to fetch the new SoftDevice, and
adding corresponding linker script for the BLE stack.

All STM32 with a UART7 also have a UART8 and vice versa, but this change
improves readability and allows for them to be independent in the future.

As already mentioned in the docs, not all constants may be available on all
ports, so this is optional to implement.

Previously specifying None as the pull value would leave the pull up/down
state unchanged.  This change makes it so -1 leaves the state unchanged and
None makes the pin float, as per the docs.