Fix warnings [-Wunused-xxx] from compilation

[cyrilgandon]

Cleaning duty, warnings are generates with

fpm build --verbose --flag '-Wunused-variable -Wunused-dummy-argument -Wunused-parameter'

Progress

• 42 unused-variable
• 15 unused-parameter
• 12/67 unused-dummy-argument
• 55/67 unused-dummy-argument

Leaving 55 unused-dummy-argument warnings unresolvable, see conversation about those.

[perazz]

LGTM, thank you @cyrilgandon.

[awvwgk]

Thanks for sharing

[jvdp1]

Thank you @cyrilgandon for this PR. I have only one minor comment regarding Python procedures. Recently, a procedure of Python >3.9 (?) was introduced in the Fortran stdlib, limiting its compilation on systems supporting most recent versions of Python. It would be nice if this issue can be avoided, hence my question below.

[jvdp1]

Based on @perazz 's answer, this PR can be merged IMO. Thank you @cyrilgandon for cleaning the code.

[cyrilgandon]

I still have some fix to do on unused-dummy-argument. This is a bit more complicated because I have to really understand what the code does for some cases

[perazz]

It seems like all comments have been addressed. Let's wait one or two days for further comments, and then merge.