Due to an old design decision runlevel S was encoded internally as '0',
meaning it was the same as halt/poweroff. If you want to run scripts at
system shutdown this was less then ideal since it meant your scripts
also ran at bootstrap.
This change is quite invasive. It introduces INIT_LEVEL (10) as the
value for runlevel S, meaning all code that parses and/or evaluates
anything for runlevel 0/S was affected and had to be reworked.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>