kevent errata for 5.6, 5.7 and 5.8

A problem with kevent(2) timers has been fixed. If triggered (which can
be done by a local unprivileged user), it would result in a kernel hang.
Patches for the kernel are available:

5.6:
http://ftp.openbsd.org/pub/OpenBSD/patches/5.6/common/032_kevent.patch.sig

5.7:
http://ftp.openbsd.org/pub/OpenBSD/patches/5.7/common/018_kevent.patch.sig

5.8:
http://ftp.openbsd.org/pub/OpenBSD/patches/5.8/common/005_kevent.patch.sig