#125 partial support for CAN-BL (AN3154) using slcan/cantact-fw

[timmy copperfield]

idk if you guys care or not, but I added in some (a bit incomplete) support for CAN-BL in my fork here: https://github.com/trollcop/stm32flash
Since CAN protocol is self-error checking, a lot of the commands that transmit checksum or XOR'd values to device are replaced with simpler versions. I added PORT_CANBUS and added things where it made sense. The basics work (RW mem, Erase, Go), but more boring stuff like read/write protect/unprotect isn't checked because I didn't need this functionality.

slcan protocol is implemented by https://github.com/linklayer/cantact-fw and my fork of it to run on STM32F072B-DISCO: https://github.com/trollcop/cantact-fw
It's a simple ascii-based thing. I'm using a subset of it. (open, close, rx/tx frames).

Regarding the changes, since I develop on Windows, I've also made some fixes to allow stm32flash to build under Visual Studio (instead of requiring/using MinGW/cygwin). That's also a separate commit in the stm32flash github fork.

Would there be any interest in either of these things or should I just keep it to myself?

Build under vstudio, minimal changes, should not affect anything: https://github.com/trollcop/stm32flash/commit/f732888b45f3971f1fb579f8fc305a0ddf265a25

CANBUS support: https://github.com/trollcop/stm32flash/commit/73ad7996fa7102e0bb5a7d91baa884a717347e06