Function check_rayintersect checks whether there is an compiled version of rayintersect.cc in the working directory, and whether the compilation has an newer time stamp than the source-code file. If not, rayintersect.cc is compiled by a call to mkoctfile(). (c) 2024-2026 fabien van mook 2026.08.20 release of this file within package "fvm-rayintersect" under GNU GPLv3+