Make scan work with new backend.

Release GIL while waiting for the GPU

Fix tests in python3.

Opt Reduce(join())

It should also not break the old cuda backend.

Port op GpuImages2Neibs to new GPU backend

Minor fixes

This avoids blocking interrupts.

use safe_to_cpu to transfer output results in op_lifter, since some ops return some results already on the cpu.

- Add opt to lift HostFromGpu through Rebroadcast
- Add broadcast pattern check on the GpuAlloc opt.

BUGFIX introduced in 4cf0f055 and merged...

That commit removed copy in Elemwise.perform(), but numpy.real return a view. This is bad if the op isn't inplace!

Mixed