I noticed xorg-server-1.5 in ~x86 this morning and upgraded to it, which resulted in an emerge looking like: libdrm-2.3.1 ... (other packages) mesa-7.1 ... (other packages) xorg-server-1.5 After this I had to re-emerge xf86-video-i810 which wasn't being loaded by X because of a missing symbol. After that, gdm would fail to start with no apparent error message. After shooting in the dark for a while I noticed that if I disabled DRI in xorg.conf gdm would start - so I re-emerged all dri-related things (and perhaps some that weren't... gdm, xf86driproto, dri2proto, xf86vidmodeproto, xf86miscproto, xf86-video-i810, libXxf86misc), ending with mesa which finally let gdm start. Reproducible: Didn't try
You should re-enable DRI if you haven't do so already. For some reason, Intel machines needs to be restarted after updating xorg, the driver must have some weird bit-banging issues. If DRI still doesn't work, please don't hesitate to reopen this bug. Thanks
Mesa has to come before xorg-server. It might be affected by version changes in some of the X libraries and protocol headers, though. I'll update all the library and proto dependencies in Mesa to pull in the latest versions.