Failed compilation with  GNU Fortran (GCC 15.1.0)


**Versions affected (tested):** Q6, Q6_esguerra, Q 5.10.1

**Operational systems tested:** MacOS (Sequoia 15.5), Debian 

**Compiler:** gfortran (gcc 15.1.0)

**Problem:** compilation fails since compiler is expecting SUBROUTINE instead of FUNCTION sigint_handler(sig_num) in qdyn.f90. 

**Solution:** rewrite the fortran code with SUBROUTINE. Or use previous version of compiler. 

