Basic support for OpenCL (experimental)

Basic support for OpenCL

Problem: OpenCL cannot import stdint.h. Temporary fix: define custom opencl_stdint.h (defines currently only int64_t `)

TODO:

• implement opencl_stdint.h
• implement shard_mem, textures, built-in functions
• avoid CUDA intrinsics (fast_div)

README.md

@@ -52,6 +52,7 @@ Without `[interactive]` you get a minimal version with very little dependencies.
 
 All options:
 -  `gpu`: use this if an Nvidia GPU is available and CUDA is installed
+-  `pyopencl`: basic OpenCL support (experimental)
 - `alltrafos`: pulls in additional dependencies for loop simplification e.g. libisl
 - `bench_db`: functionality to store benchmark result in object databases
 - `interactive`: installs dependencies to work in Jupyter including image I/O, plotting etc.