Late USB enumeration could clear settings after they had been set.
Now fixed by not clearing some settings on init.
RX was blocking if received characters were not being processed, so
CTRL-C would not be picked up. Now "fixed" by not blocking, but
instead discarding incoming characters if they overflow the buffer.
New USB HAL is quite a bit improved over previous one. Now has better
callbacks and flow control.
REPL over USB CDC now works as before, except for soft-reset (since USB
driver uses malloc...).
Damien George