Support for PowerBook 1xx (mac68k) batteries via envsys(4).

Hi,

Please see referenced patch for review:

http://ftp.netbsd.org/pub/NetBSD/misc/nat/pbbat.diff

It adds support for PowerBook 1xx batteries based on acpibat(4).

The only thing I don't like is the attachment via aed(4) and the way it was 
handled (blindly attach at aed) so I'm hoping there will be alternative
suggestions.  It doesn't have a bus address as such so my initial
pbatt* at adb? was not successful and competed with the aed(4) attachment.

I'd really like to wrap up the attachment in aed in #ifdef conditionals but 
was unable to find/use NPBBAT > 0.

I've opened up a PR to track the progress: PR port-mac68k/59228.

Best regards,

Nat