Firmware BMP with ENABLE_DEBUG=1 will print WARN and INFO as before.
PC-Hosted BMPwill alway print to stderr. Warn is printed unconditional,
INFO, GDB, TARGET, DONGLE and WIRE will print if their appropriate bit in
cl_debuglevel is set via the -v verbose command line argument.
INFO will go to stdout with -t or -l.
Complements #204.
STLinkV2-1 has F103CB on board! F103C8 on older Stlinks can use upper flash
with hopefully acceptable error rate.
For F103C8 devices, user has to give the force option to dfu-utils.
