Someone

!!! All ebuilds that could satisfy ">=x11-libs/gtk+-2.11.5" have been masked.
!!! One of the following masked packages is required to complete your request:
- x11-libs/gtk+-2.12.0 (masked by: ~x86 keyword)
- x11-libs/gtk+-2.12.0-r2 (masked by: ~x86 keyword)
- x11-libs/gtk+-2.12.0-r1 (masked by: ~x86 keyword)

For more information, see MASKED PACKAGES section in the emerge man page or 
refer to the Gentoo Handbook.
(dependency required by "gnome-base/libgnomeui-2.20.0" [ebuild])