fleshed out rest of fileops interface; read now takes into consideration current file position (so the display can be read in multiple operations, and indiate EOF correctly), seek (really just to facilitate rewind), and unlink (to facilitate dropping from system at runtime).

correct logic hazard in latch and load nybble; was transitioning control lines at the same time as enable, causing spurious behaviour on less-tolerant displays

improve timing parameters in init sequences for better display compatibility

correct (row,col) -> address calculation; affects 4-line displays

update comments in header and readme

libuavcan: Forgot to change define

FS: Add logic to detach a file structure from a file descriptor.  This is for use only within the OS.  It permits an open file or driver to be used across multiple threads.

lcd/Kconfig, Make.defs: Remove dependency of CONFIG_LCD_NXDRIVER for building non-graphic, SLCD drivers.

get I2C working for STM32L4

1-wire:  Initialization/uninitialization functions are not use MCU-independent up_ naming.  Should use STM32-specific stm32_ naming.  These are not globally accessible but only accessible from STM32 board logic.

get I2C working.  some more work regarding clocking computation is needed, as is some inhertited 'todo's from the basis code.  but it does work with the devices tested so far.

STM32 CAN: Add support for both RX FIFOs

Additional configuration option to enable SST26 driver debug output.  Using comming FS debug output generates too much output.

complete logic in 'create stack' and 'use stack' to support stack coloration.  Fix some booboos breaking compatibility with TLS in libc.

altered pin defs for I2C pins; these needed to be specified as open-drain (otherwise they are push-pull)

complete logic in 'create stack' and 'use stack' to support stack coloration.  Fix some booboos breaking compatibility with TLS in libc.

Update Nucleo F303RE and STM32F4Discovery uavcan configurations