Changes

Porting pdf_closure subroutine with OpenACC (#1059)

* Porting pdf_closure subroutine with OpenACC

OpenACC directives are added to pdf_closure subroutine. The necessary
structured data region is also added for optimzing data movement across
kernels. There is opportunity to task parallelize using streams and
will be explored in the future.

Answers are bit for bit.

* Fixing the copyin directives

* Making work without managed memory.