gtk-doc dependency introduced by bug 398999 is now only needed with USE="doc". autotools.eclass has since been updated not to fail if gtkdocize is missing: http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/eclass/autotools.eclass?view=log#rev1.145
+ 29 Mar 2015; Justin Lecher <jlec@gentoo.org> memphis-0.2.3.ebuild: + Move dev-util/gtk-doc dep behing USE=doc, #544136 +