v.5.8.0.1
It's just a minor update for v.5.8.0:
- fix compilation for GCC-9 (so that GCC 9 through 13 can be used for to build SO-5.8.0, more older versions of GCC are not checked);
- small fixes for typos in Doxygen-related comments, some examples are extended/added in/to Doxygen comments.