eutils.eclass: preserve_old_lib() and preserve_old_lib_notify() shouldn't work when ${FEATURES} contains "preserve-libs". Portage >2.2_pre contains internal functionality used to preserve libraries. It has significal improvements over preserve_old_lib() and preserve_old_lib_notify(), e. g. it automatically deletes unneeded libraries. It is enabled when ${FEATURES} contains "preserve-libs".
Created attachment 143530 [details, diff] Patch to eutils.eclass
there's no point in echoing things with einfo since the user could care less http://sources.gentoo.org/eclass/eutils.eclass?r1=1.296&r2=1.297