Rip out APM dependency

APM is dead; make it optional for sleepd.

We add the Make option 'USE_APM', defaulted to 1. To disable APM, build
with this option undefined:

  make USE_APM=
Use sysfs instead of procfs.
Merge.
Fix the ACPI backend.
If battery percentage is -1, don't hibernate as probably something's wrong.
Fix Makefile.
Add upower support
Update the manpage to not mention deprecated HAL
Update the dependencies
Use debhelper 9.
Update the description
Update rules
Merge.