Annotate LLVM-IR for all parallel loops

  This change allows to annotate all parallel loops with loop id metadata.
  Furthermore, it will annotate memory instructions with
  llvm.mem.parallel_loop_access metadata for all surrounding parallel loops.
  This is especially usefull if an external paralleliser is used.

  This also removes the PollyLoopInfo class and comments the
  LoopAnnotator.

  A test case for multiple parallel loops is attached.