was a bit unstable under ubuntu/alsa so added some mutex protection around fifo access that is shared by callsbacks and tx/rx processing threads.  Alsa now seems more stable.
was a bit unstable under ubuntu/alsa so added some mutex protection around fifo access that is shared by callsbacks and tx/rx processing threads.  Alsa now seems more stable.

git-svn-id: 567ceadc8c7dca9f342cfd1fdb923dd411579874@1015 01035d8c-6547-0410-b346-abe4f91aad63

freedv/freedv,freedv/freedv,freedv/freedv