Signal related functions (flush_signal, allow_signal and
signal_pending) moved from include/linux/sched.h to
include/linux/sched/signal.h in 4.11.0:
http://elixir.free-electrons.com/linux/v4.10.17/source/include/linux/sched/signal.h
As a result, this module did not build in 4.11 on my Arch system.
This updates the includes to allow this module to build on 4.11.