[AD] OSS driver blocking

["Trent Gamblin" <tmg@xxxxxxxxxx>]

I don't know if there is a reason for it or not, but the OSS sound
driver blocks when something else is using the sound card, and waits
until it is finished. Shouldn't it just fail to initialize the sound
card and move on? If so, all that needs changing is unix/uoss.c, line
193 to

oss_fd = open(uconvert_toascii(_oss_driver, tmp1), O_WRONLY | O_NONBLOCK);