Allow unix:<screen> style display names again.
Allow unix:<screen> style display names again.

https://bugzilla.novell.com/show_bug.cgi?id=289007
This notion is used in a lot of scripts.

OpenInkpot-archive/iplinux-libxcb,topcat/xcb-win32,topcat/xcb-win32,stapelberg/libxcb,OpenInkpot-archive/iplinux-libxcb,topcat/xcb-win32,stapelberg/libxcb,topcat/xcb-win32,stapelberg/libxcb,topcat/xcb-win32,OpenInkpot-archive/iplinux-libxcb