[Refactor] Generalize parallel code generation

  + Generalized function names and comments
    + Removed OpenMP (omp) from the names and comments
    + Use common names (non OpenMP specific) for runtime library call creation
      methodes
  + Commented the parallel code generator and all its member functions
  + Refactored some values and methodes

Differential Revision: http://reviews.llvm.org/D4990



git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@219003 91177308-0d34-0410-b5e6-96231b3b80d8