Revert "Revert "disable /dev/tty copying. it causes conflicts with spawning julia processes""

This reverts commit 30d0897c79f48ee883589abea0bbc319240c44cb.

This has been causing segfaults on OSX builds.  Reverting this reversion fixes the issue.
Merge pull request #25 from JuliaLang/sf/uv_handle_segfault

Fix segfaults on OSX