display control by apm -d.
- Remove APM_DEBUG to avoid re-build kernel with such a unspported optioin.
- Introduce new denug flag `debug.apm_debug' which can be controlled by
sysctl interface and loader by setting like "debug.apm_debug=1", you
will get debug messages from APM driver.
- Add some enhancements from linux on display control by apm -d. I'm
expecting that we can see some improvements on some laptops where
apm -d doesn't work correctly so far.
Reviewed by: -mobile and -current folks (no objection)
Suggested by: Susumu WAKABAYASHI <susumu@wakabaya.net>
8000a5797e