I was upgrading xf86-video-i810 from 1.4.1.3 to 1.5.1.0 and it failed because randrstr.h was missing. After some digging, I upgraded xorg-server from 1.0.1-r3 to 1.0.2-r3 and it had the file (/usr/include/xorg/randrstr.h), which led to a successful upgrade. So the ebuild for xf86-video-i810-1.5.1.0 should list xorg-server-1.0.2-r3 (I don't know if previous -rX have it) as a dependency. Thanks, Alberto
Fixed, thanks!