TODO

- Addy requests more prun-like options
- Optional pdsh.conf file for configurable system wide defaults
- Improve xpoll() interface??
- autoconf putenv
- support long options
- command line check for fanout > posix thread limit
- option to allocate all threads/mem before executing command
  - important so that if fanout is too large, commands won't
    be started and killed halfway through.
- bproc rcmd module
- ssh module should use pipecmd