This implementation creates a temporary file (suffixed with .tmp) and
renames it to the expected file name when the file is closed.
If the renaming fails, the destination file is removed and renaming is
tried again to handle cases where renaming over an existing file is not
supported by the underlying OS.
When creating an atomic write stream, the file is only created once it
is closed.
This can be done using a temporary file.
This commit only adds the API but not the proper implementation.
The Vita SDK gained support for dirent at the end of 2017. There is no
need to have our own version anymore.
DrivesPOSIXFilesystemFactory allows to specify the contents of the
pseudo-root file system node. There is no need to hardcode them in
posix-fs.cpp anymore.
