Replace the final two files from Tom LeFebvre, ExtFtn.h and IntrinsicFunctions.f

At this point, all four files that were pulled from WRF have been replaced. I haven't changed the README files for src yet, however, because I think Jonathan H. did some edits there that hasn't been pushed back to PyAOS/aoslib. So, all the WRF files are now replaced by the NOAA versions and so all the code files in src are from NOAA and are in public domain.

The other reason I'm doing this pull request is I've never done one before, so this is my attempt to see how it works.