Remove catch clause which is never executed
pid_t could be possibly not int
Refactor get_machine_status
Fix deadlock on linear_mixer::stop()
Remove volatile
Refactor linear_mixer::mixer_loop
Merge pull request #406 from gintenlabo/fix-uninitialized-values

Fix issue #377 (get_status returns uninitialized values on some platform)
Merge pull request #407 from gintenlabo/remove-volatile

Remove volatile (fix issue #394)