This prevents any background sub-command executed from inheriting
the descriptor & lock (and making vi think that someone else is
editing the file when it re-edits).
Remembered from: An OpenBSD commit message from May '99
this will make it less likely to misinterpret arrow keys as seperate
keys when running over anything slower than a console.
This has been talked about for a while, I hope it's long enough but not
too long to be annoying.
