Looks like GpuRaySensor.hh went missing in Gazebo 1.3. I checked out the lastest source from the repo:
~/src/gazebo$ ls gazebo/sensors/Gpu*
gazebo/sensors/GpuRaySensor.cc gazebo/sensors/GpuRaySensor.hh
But in my installed (Ubuntu package), there is no more GpuRaySensor:
/usr/include/gazebo-1.3$ ls gazebo/sensors/Gpu*
ls: cannot access gazebo/sensors/Gpu*: No such file or directory
Pretty sure it was there in 1.2 and earlier as I had compiled worked on an extension to the base GpuRaySensor class.