* Use "itimer" instead of alarm when available for higher resolution
  timing in setTimer/getTimer.

* Determine more pthread targets which may allow SIGALRM to be used
  beyond Linux for multiple timer instances.

* Optional support for Posix timers rather than alarm or setitimer
  for getTimer/setTimer when available on target platform.

* Make SharedFile use a ThreadKey to save a file position marker
  automatically for each thread.  And use pread/pwrite for better
  performance.

