Fix signal handler

[elfring]

The functions "ioctl" and "exit" do not belong to the list of async-signal-safe functions.
I guess that a different program design will be needed for your functions "gpm_winch_hook" and "killed".

[telmich]

@elfring It is nice to point out - are you going to submit a PR later on?

[elfring]

Would you like to consider software design options like the following?

• Self-pipe trick
• Signal-safe locks
• sigwaitinfo()

[telmich]

In theory yes, the question is more about who is going to implement them, I guess

[elfring]

Are you willing to dedicate another thread for receiving of notifications by the function "sigwaitinfo" or "select"?

[vapier]

that random link is broken now, so here's the official list of async-signal-safe functions.

wrt kill, none of those funcs are safe -- printf (via CLEAR), fprintf, or exit. I/O streams can be holding locks when the signal comes in, and exit can run atexit handlers which can do anything. so that func should be changed to use write;fsync;_exit and it should be fine.