Autotools -> cmake for commit ee258ec2629024f966526e5ba0c44b18ad8bbaf1

Original commit message:
  Add ${prefix}/share/pocl/include to the --cflags of pkg-config because
  some external clients (such as TCE) of libpocl.so or pocl-standalone
  might need to refer to pocl.h.
Fix a few target properties on llvmopencl
Get rid of LIBPOCL_LOCATION and POCL_LIB_SUFFIX

The LOCATION property is deprecated in cmake 3.0.0, and there is a much
more elegant way to do this, without guesswork.