Note that this API seems broken beyond repair to me.
It *might* crash. I cannot fix it.

This partly reverts commit 8689e8be.
Didn't meant to include this change in commit.

- Add stats-change variable for input to inform when statistics are computed
- Use that variable in qt4 interface to update statistics so no need to loop
  with timer ( ticket #1365)

We don't want to leak descriptors to child PROCESSES (!= threads) such
as the pseudo-CGI interface. The socket wrappers ahve already been doing
that for a while. Unfortunately, there are still many "leaks", through
underlying libraries, opendir(), fopen(), etc. And then, this is not
thread-safe (we leak if another thread calls fork() between open() and
fcntl()). This is a well-known limitation in POSIX anyway.