* Header files moved into include/stlink
* doc/tutorial.{pdf/tex} converted to markdown for rendering by github and easy editing
* Remove `stlink-` suffix from some C source files and move into `src/tools`
* Fixup #318 serial print in stlink probe with trailing zeros
* Refactor stlink-usb.h with some doxygen-style comments
* Refactor some pieces of stlink_open_usb
Remove st-term from the list of the targets for MinGW.
st-term uses termios and would require a rewrite to have
it compile on MinGW. Also remove cleanup signal handlers
in gdb-server for MinGW to compile.