Bug#950346: please mark some more symbols as optional

[Matthias Klose]

Package: src:libsavitar
Version: 4.4.1-1
Tags: patch

please mark some more symbols as optional, seen when building with -O3 on
ppc64el and s390x.

patch at
http://launchpadlibrarian.net/462915998/libsavitar_4.4.1-1_4.4.1-1ubuntu1.diff.gz