Added functionality to the SYS_SYSTEM semihosting call.

There seems to be a few missing semihosting calls.  I
am not sure why this one is actually missing, since it
seems simple enough to implement.  It was tested using
an HTC HD7 connected to openocd through a "home brew"
ftdi 4232H board.

Change-Id: Ie17dc96c6d48227a3dc9ff1e21201a85498a10b1
Signed-off-by: Brandon Warhurst <roboknight@gmail.com>
Added functionality to the SYS_SYSTEM semihosting call.

There seems to be a few missing semihosting calls.  I
am not sure why this one is actually missing, since it
seems simple enough to implement.  It was tested using
an HTC HD7 connected to openocd through a "home brew"
ftdi 4232H board.

Change-Id: I0d0979b1da588fbe9dd7fffea570c83f7d6aa85e
Signed-off-by: Brandon Warhurst <roboknight@gmail.com>
Merge branch 'master' of ssh://openocd.zylin.com:29418/openocd