Adaptions for LLVM 3.3 / SPIR

Adaptions for LLVM 3.3 / SPIR

Handle the fact that several include files are moved from llvm/ to
llvm/IR/ in LLVM 3.3.

"__attribute__((always_inline)) inline" no longer works as intended,
and is replaced by "inline __attribute__((always_inline))".

For LLVM 3.3, the target is changed from "nvptx" to "spir", and
built-in address space qualifiers are used. For now, the built-in
types image2d_t, image3d_t, sampler_t, and event_t are overridden by
defines.

Signed-off-by: Dag Lem <dag@nimrod.no>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>
Tested-by: Xing, Homer <homer.xing@intel.com>
Tested-by: Yang, Rong R <rong.r.yang@intel.com>