simple C client example of using SBP

[denniszollo]

Should be for a normal PC with a POSIX serial library (not an embedded target). Would be great if we got this in before 1.0.

cc @mfine @cbeighley @mookerji @fnoble

[henryhallam]

Serial code example: https://gist.github.com/henryhallam/31810c9ef54642c518d3 (includes various fault-handling stuff that is overkill for the SBP example)

[henryhallam]

Rates in excess of B115200 are supported on Linux and I think Windows but not OSX. You can use some kind of IOKit workaround, but I think it would be OK to just guard it with #ifdef __linux__ and note that OSX users will have to use a lower baud, implement the workaround, or use FTDI's aliasing crap.

[gsmcmullin]

From pyserial it looks like OSX is quite easy to support:

elif plat[:6] == 'darwin':   # OS X

    version = os.uname()[2].split('.')
    # Tiger or above can support arbitrary serial speeds
    if int(version[0]) >= 8:
        def set_special_baudrate(port, baudrate):
            # use IOKit-specific call to set up high speeds
            import array, fcntl
            buf = array.array('i', [baudrate])
            IOSSIOSPEED = 0x80045402 #_IOW('T', 2, speed_t)
            fcntl.ioctl(port.fd, IOSSIOSPEED, buf, 1)
    else: # version < 8
        def set_special_baudrate(port, baudrate):
            raise ValueError("baud rate not supported")

[ungureanuvladvictor]

PR here: #193