Remove APM BIOS support

APM BIOS was relevant only to early laptops (approximately P166 or
P200 and slower). These have not been relevant for a long time, and
this code has been untested for a long time (as far as I can
tell). The APM compat code in ACPI and the apm(8) command is not being
retired. Both of these items are still in use (apm(8) is more
scriptable than the replacement acpiconf, for the most part). This has
been commented out of i386 GENERIC since 2002. This code is not
relevant to any other port.

Discussed on: arch@