OpenMP unroll and tile directive

[yanyh15]

OpenMP unroll directive:

The syntax of the unroll construct is as follows:  

#pragma omp unroll [clause] new-line 
    loop-nest
  
where loop-nest is a canonical loop nest and clause is one of the following:  

full 
partial[(unroll-factor)]
       
where unroll-factor is a positive integer expression that is a compile-time constant.

• add the directive and clause to the ompparser (Xinyao)
• add sage nodes for unroll directive, SgOmpUnrollStatement and its clauses (Patrick)
• Enhance ompConstruction to connect ompparser to REX (Xinyao)
• Implement the transformation using the unroll function from ROSE sageInterface (Patrick)
• Create test cases and add to the CI test (Xinyao and Patrick)
• add tiling support the same time using the same procedure since tile construct is also very simple and similar (Patrick and Xinyao)

[pflynn157]

This should be fully working. Changes are in patrick/all