Always output seccomp error messages to stderr

Always output seccomp error messages to stderr

Also now we always use WriteToStderr and move comments to
appropriate positions.

TEST=trybots
BUG=359285
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=262829

[hamaji, 2014-04-09 18:11:00]

Per https://codereview.chromium.org/196793023/

[jln (very slow on Chromium), 2014-04-09 18:57:55]

lgtm, thanks!

[jln (very slow on Chromium), 2014-04-09 19:53:44]

On 2014/04/09 18:57:55, jln wrote:
> lgtm, thanks!

Also, FYI, for Chromium bugs, just do BUG=bug_number in the CL description. This
way it becomes a clickable link.

[hamaji, 2014-04-09 20:12:46]

The CQ bit was checked by hamaji@chromium.org

[commit-bot: I haz the power, 2014-04-09 20:12:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hamaji@chromium.org/231423002/1

[hamaji, 2014-04-09 20:14:29]

On 2014/04/09 19:53:44, jln wrote:
> On 2014/04/09 18:57:55, jln wrote:
> > lgtm, thanks!
> 
> Also, FYI, for Chromium bugs, just do BUG=bug_number in the CL description.
This
> way it becomes a clickable link.

Done. IIRC Mark told me to use full URLs for NaCl repo, but yes, this patch is
for Chrome repo. Fixed, thanks!

[commit-bot: I haz the power, 2014-04-09 21:49:52]

Change committed as 262829