os: drop unneeded DDXOSVERRORF conditional
This conditional practically only controls whether we have an pointer, where DDX can plug in it's own VErrorF() handler (currently only xwin doing that). The cost of having it even when DDX doesn't use it, is really negligible: it's just one pointer and an extra non-null check on it per VErrorF() call - a very cold path. Strangely, xwin has extra
Getting rid of this unnecessary complexity that really hasn't any practical gain.
Signed-off-by: Enrico Weigelt, metux IT consult info@metux.net