On the one hand, we stop using OpenC here. On the other, we no longer
use an atomic create and obtain file handle API -- just as we don't on
Windows yet.
This is a stepping stone to removing back and forth conversions of path
names when generating unique names and also towards the use of native
APIs for creating and obtaining a file handle atomically.
Reviewed-by: Gareth Stockwell
Reviewed-by: Shane Kearns
(cherry picked from commit 63bb67d3107b03f399cddf4c9cca9c7eb347b62d)
Change-Id: I97b3b6179dff053807acc8d4469fdf57f57f68a6
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>