oss: remove redundant assignments
oss: split some long lines
oss (oss_refill_stream): move code under if(got > 0)
oss (oss_stream_start): lock mutex before checking
oss: prevent decreasing position counter
oss: remove nfds variable from struct cubeb
oss: move buffer allocation from oss_refill_stream() to rebuild()
oss: limit thread stack size