Some masked packages in x11-proto/ (they are consolidated in x11-base/xorg-proto) do not get removed with "emerge --depclean" since the package was not revbumped. Manual rebuild of package is required. Do other versions of the same package require a revbump, too?
I'm not sure why it would require rebuild, since this was only a DEPEND change and not RDEPEND. This will also be solved by (very) imminent Qt4 masking.
The package is listed when I run "emerge -avc" for the following packages, was it depend some longer time ago? x11-proto/videoproto-2.3.3-r1 pulled in by: dev-qt/qtgui-4.8.7 requires >=x11-proto/videoproto-2.3.1-r1[abi_x86_64(-)] x11-proto/inputproto-2.3.2-r1 pulled in by: dev-qt/qtgui-4.8.7 requires >=x11-proto/inputproto-2.2-r1[abi_x86_64(-)] x11-proto/videoproto-2.3.3-r1 pulled in by: dev-qt/qtgui-4.8.7 requires >=x11-proto/videoproto-2.3.1-r1[abi_x86_64(-)] x11-proto/xextproto-7.3.0-r1 pulled in by: dev-qt/qtgui-4.8.7 requires >=x11-proto/xextproto-7.2.1-r1[abi_x86_64(-)] x11-proto/xineramaproto-1.2.1-r2 pulled in by: dev-qt/qtgui-4.8.7 requires >=x11-proto/xineramaproto-1.2.1-r1[abi_x86_64(-)]