Better syscalls implementations for ChibiOS

Nothing particular is needed: just add this package to your dependencies and it should automatically work. If you want to use stdout, for example for printf (3), you should define STDOUT_SD to the stream you want to use. Same goes for stdin, using STDIN_SD.

One way to do it is to put the following in your board.h:

#define STDOUT_SD SDU1
#define STDIN_SD SDU1

You could also do it in your Makefile by adding the following line:

UDEFS = -DSTDOUT_SD=SDU1 -DSTDIN_SD=SDU1