Handle renames of RVars
gpuapi -> gpu_api
gpuapi -> gpu_api
Add an outermost scheduling point

so you can schedule things at the same loop level as another func
Indentation fix.
<root> -> __root to keep in line with other magic names
__buf_size of scalar buffers is elem_size
Add ability to schedule scalar stages on gpu without using a dummy var

Relies on the outermost scheduling point just introduced.