Summary:
Timeout has been broken by my previous patch.
The timeout event was not being processed correctly,
as such hanging processes would not be killed as they should
have been.

This corrects it.

Test Plan:
./validate

~/ghc/testsuite/timeout/install-inplace/bin/timeout.exe 10 "sleep 10000s"

Reviewers: austin, RyanGlScott, bgamari

Reviewed By: bgamari

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2880

GHC Trac Issues: #13004