Revert "Remove useless $out parameter from SkinTemplate::prepareQuickTemplate()"

This reverts commit 404939b9c272bd12a62bb47f7ca452368b7f20ca.

Lacked sufficient deprecation process (no notice, no one checked
existing skins), resulting in a fatal in at least one skin (BlueSky).

Change-Id: Id009f6ac05ebcb3cd1f739b1b46e810ddacf29af
Merge "Revert "Remove useless $out parameter from SkinTemplate::prepareQuickTemplate()""