Centralized Fortran logging

[aoymt]

Summary

This pull request introduces a shared logging facility in m_common, then migrates a large portion of the codebase from write usage to that API. The goal is more consistent, controllable diagnostics across TurboRVB tools and drivers.

What changed

New modules and provenance

• Logging stack: The files stdlib_logger.f90, stdlib_ascii.f90, stdlib_kinds.f90, and stdlib_optval.f90 are taken from the Fortran standard library (fortran-lang/stdlib), copied into src/m_common/, and adapted locally so they build and integrate cleanly inside TurboRVB (this is not a full stdlib subtree).

• Project-specific layer: logger_io.f90 is a TurboRVB-specific thin wrapper around stdlib_logger for convenient call sites. tostring.f90 (M_tostring) provides generic-to-string conversion used by that wrapper; it follows a pattern described on Fortran Wiki — tostring.

• Build: m_common/CMakeLists.txt is updated to compile and link these new sources.

Call-site migration

• Fortran sources across major areas (a_convertfort10, a_convertfort10mol, a_convertfortpfaff, a_makefort10, a_prep, a_readforward, a_tools, a_turborvb, b_complex, and many m_common utilities) now route diagnostics through the new logging layer instead of scattered direct output, with related cleanups where output paths were touched.

Licensing

Vendored stdlib-derived sources remain subject to the Fortran stdlib license (typically MIT). The authoritative license text is in per-file notices where present.

Notes

• The diff is wide but largely mechanical: the same information is routed through the new logging API. Spot-check a few representative binaries (e.g. prep, turborvb, a couple of a_tools programs) for expected stdout/stderr behavior and log levels.
• Confirm MPI / parallel runs still produce sensible output (e.g. no unintended duplication or lost messages on non-root ranks), if that was a design goal of this branch.
• Limitation: The present implementation of logger_io do not directly handle arrays; they are printed elementwise via do-loop.