Fortran auto-build

[chiaraMaHe]

Auto-Build system for the Fortran interface.
Use --enable-fortran while configure

All these boxes must be checked by the reviewers before merging the pull request:

As a reviewer please read through all the code lines and make sure that the code is fully understood, bug free, well-documented and well-structured.

General

• The reviewer executed the new code features at least once and checked the results manually

• The code follows the t8code coding guidelines

• New source/header files are properly added to the Makefiles

• The code is well documented

• All function declarations, structs/classes and their members have a proper doxygen documentation

• All new algorithms and data structures are sufficiently optimal in terms of memory and runtime (If this should be merged, but there is still potential for optimization, create a new issue)

Tests

• The code is covered in an existing or new test case using Google Test

Github action

• The code compiles without warning in debugging and release mode, with and without MPI (this should be executed automatically in a github action)

• All tests pass (in various configurations, this should be executed automatically in a github action)

  If the Pull request introduces code that is not covered by the github action (for example coupling with a new library):

  • Should this use case be added to the github action?
  • If not, does the specific use case compile and all tests pass (check manually)

Scripts and Wiki

• If a new directory with source-files is added, it must be covered by the script/find_all_source_files.scp to check the indentation of these files.
• If this PR introduces a new feature, it must be covered in an example/tutorial and a Wiki article.

Licence

• The author added a BSD statement to doc/ (or already has one)

[holke]

Looks good.
I can configure and build with and without enable-fortran.
The fortran interface is build.

Only one question:
Is this commented out intentionally?
"#include t8_fortran_specific.mk"

[holke]

What does the "mo" in the name stand for?

[chiaraMaHe]

it stands for 'module'. There was an error because there were two files with the name t8_fortran_interface.f90 in the old version and so it was named with the mo inside of the name. However, as there is now only one file with this name, I can change that

[holke]

Will this be activated in follow-up PRs or should this be activated now?

[chiaraMaHe]

Will change that

[holke]

[ ] Should this use case be added to the github action?

Yes it should, i would propose to activate "enable-fortran" in all test cases by default.
will open a new issue.

Edit: see #1214

[jmark]

This PR is now covered by: #1255