windows: make uv_spawn() failure more predictable

* It will now report some types of errors synchronously, to bring it on
  par with uv-unix. Fixes #865.

* Failure to find the target executable will now set up stdio pipes
  correctly, so the user can assume that when uv_spawn() returns 0 these
  pipes will never trigger asserts in libuv's guts.
process: make the 'status' parameter for exit_cb an int64_t

This means we no longer have to strip the high bit from the process exit
code on Windows, which is problematic because an unhandled SEH exception
can make a process exit with a status code that has the high bit set.
2013.08.24, Version 0.11.9 (Unstable)

Changes since version 0.11.8:

* fsevents: share FSEventStream between multiple FS watchers, which
  removes a limit on the maximum number of file watchers that can be
  created on OS X. (Fedor Indutny)

* process: the `exit_status` parameter for a uv_process_t's exit
  callback now is an int64_t, and no longer an int. (Bert Belder)

* process: make uv_spawn() return some types of errors immediately on
  windows, instead of passing the error code the the exit callback. This
  brings it on par with libuv's behavior on unix. (Bert Belder)
Now working on v0.11.10