serial terminal support

Hello.
I have put up an effort to make an easy to use serial terminal via stlink, that doesn't require any reflashing of the STLINK's MCU and adding wireporn. 
Basically, st-term just scans sram for a struct with known magic and uses two buffers within the struct to communicate with the firmware. 
A proof of concept code for the firmware is available here: https://github.com/nekromant/antares/blob/master/src/lib/stlinky/stlinky.c
A more in-detail description can be found here: http://ncrmnt.org/wp/2013/05/06/stlink-as-a-serial-terminal/
st-term is ugly in places, but works fine so far