merged

avoid "exec" to change the winpid;

clarified check of root process on Windows (NB: the winpid is less stable than the Cygwin/Posix pid, so it needs to be "patched" into the the bash script, instead of bash_process.c);

fast approximation of test for process group (NB: initial process might already be terminated, while background processes are still running);

clarified signature;

rebuild executable for x86_64-darwin;

clarified command-line;

update Linux base-line;

tuned comments;

tuned signature;