Not just because it's what the cool kids are doing --- it also lets us
simplify the inner loop and decouple it from whatever systems want to
be woken to perform some activity if there's data to be read on some fd.
Currently this is just used to clean up the existing signal handling,
keychord, and property service code.
Change-Id: I4d7541a2c4386957ad877df69e3be08b96a7dec5
Also make important events in init's life NOTICE rather than INFO,
and ensure that NOTICE events actually make it to the kernel log.
Also fix the logging so that if you have a printf format string
error, the compiler now catches it.
Also give messages from init, ueventd, and watchdogd distinct tags.
(Previously they'd all call themselves "init", and dmesg doesn't
include pids, so you couldn't untangle them.)
Also include the tag in SELinux messages.
Bug: 19544788
Change-Id: Ica6daea065bfdb80155c52c0b06f346a7df208fe
