Posix: Improved FD functions.
Posix: Improved FD functions.

"open:..." accepts more readable flags, and optionally the mode (for
when the 'create' flag is used).  "open:...", "read-fd:..." and
"write-fd:..." all throw an exception on an error.

stevefolta/trylon,stevefolta/trylon,stevefolta/trylon,stevefolta/trylon,stevefolta/trylon