This Gnome software uses both DISABLE_SINGLE_INCLUDES and DISABLE_DEPRECATED which breaks with stable libunique. I have patched this out in the ebuild. The tree commit was approved by Leio; he reports that this patch or at least a description of the problem should be relayed upstream.
Sorry, I prepared the patch to adapt configure to old libunique but forgot to really downgrade my libunique version (that got installed when upgrading locally using overlay) when I recompiled evolution
Sent: https://bugzilla.gnome.org/show_bug.cgi?id=621544
*** Bug 323969 has been marked as a duplicate of this bug. ***