Bug#923639: mark one more symbol as optional when built with -O3

[Matthias Klose]

Package: src:ucommon
Version: 7.0.0-16
Tags: patch

Mark one more symbol as optional when built with -O3.

patch at
http://launchpadlibrarian.net/413499090/ucommon_7.0.0-16_7.0.0-16ubuntu1.diff.gz