dev-libs/amdgpu-pro-opencl: new package

dev-libs/amdgpu-pro-opencl: new package

Bits of AMDGPU-Pro providing OpenCL support. Work fine with the Open Source
amdgpu stack, the only catch is that one also needs the proprietary version of
libdrm_amdgpu which could conflict with the one from x11-libs/libdrm.
Fortunately, this can be easily worked around by hacking rpath of the OpenCL
library. Will hopefull integrate well with the rest of AMDGPU-Pro once it has
made it into the tree.

Please note that this driver works ONLY when loaded by dev-libs/ocl-icd;
there is no possibility for it to operate as an independent implementation.

For the time being this is a 64-bit only package. That said, although AMD
only supports AMDGPU-Pro on amd64 the driver pack does include 32-bit binaries
 - so multilib support might be added later.

Inspired-By: Arch Linux opencl-amd AUR package
Package-Manager: Portage-2.3.6, Repoman-2.3.1