add support for openacc in both build systems

[rem1776]

Description
Adds openacc options and compiler checks to both build systems.

-DOPENACC=on for cmake
--enable-openacc for autotools

There is some changes to the license file because i borrowed the m4 function from some other code (which is pretty common for m4 stuff).

How Has This Been Tested?
tested with gcc and nvfortran with autotools.

for cmake nvfortran needs #1743 updated and merged to work properly.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes