write testsuites for autopar's code generation part

After triggering autopar's code generation part after Graphite, I write some testcases for judging whether this part works correctly. Now the simple tests is located at testsuites/gcc.dg/graphite/graphite_autopar. These test cases will PASS all the 9 checkings (3 checkings per test). Unfortunately, the reduction tests (I didn't include in the testsuites) will fail when collecting reduction information. I'll work with Razya to findout why.

Basic plans:

• Regression test for the patch(split autopar) for trunk.
• Try to merge/update Graphite's autopar code generation part with trunk (This part need some time, maybe I'll try to findout if we can do this appropriately first).
  
• Testsuites of autopar in trunk didn't actually run (just compile and analysis dump file), so maybe I'll submit a patch for that.