The rc system aggressively caches the contents of /etc/rc.conf in order to
improve boot performance; this produces arguably astonishing (non-)results
if /etc/rc.conf is modified during the boot process.

Since performance considerations make it infeasible to automatically detect
if the cached /etc/rc.conf parameters should be invalidated, provide a
mechanism for explicitly requesting that /etc/rc.conf be reloaded: Catch
SIGALRM and reload /etc/rc.conf if it is received.

Discussed on:	freebsd-rc
MFC after:	3 days