handle_recursive: fix race condition if threads are used
Requires thread-local storage.
Another solution would be a mutex, but this is slower and more
complicated and might cause issues with some programs.
- [DH] NEWS
- [DH] configure.ac
- [DH] m4/README
- [DH] m4/ax_tls.m4
- [DH] src/coloredstderr.c