Fix DSA for function parameters.


Function parameters are erroneously detected as shared.

This test comes from the gcc testsuite (omp-single-3), and clang-omp (a65de2d1) complains that `a` and `b` are not private while they actually are.
The error message is the following : `error: copyprivate variable must be threadprivate or private in the enclosing context`

    extern void abort (void);
    
    void
    single (int a, int b)
    {
      #pragma omp single copyprivate(a) copyprivate(b)
        {
          a = b = 5;
        }
    
      if (a != b)
        abort ();
    }
    
    int main()
    {
      #pragma omp parallel
        single (1, 2);
    
      return 0;
    }

This happens because `isFunctionOrMethodVarDecl` only check for `Decl::Var` and not for `Decl::ParmVar`.
According to the documentation it's the expected behaviour, so I guess the additional check belongs in `SemaOpenMP`.