io/io: add comments for reserved pins
debug/break: add _BREAK() macro
debug/assert: use _BREAK()
main: use wdt_disable directly; record MCUSR value
debug/reset: remove reset_defuse
debug/stdfile: combine fdevopen/fclose for standard streams
lcd/lcd: track initialization and don't block if uninitialized
io/uart: handle LF/CR transformations in stdfile wrappers
obd/stn1110: don't use uart timeouts
obd/stn1110: transform \r to \n and back