[CFT] acpi_ibm event handler

[Mitsuru IWASAKI]

Hi,

I've noticed that brightness up/down keys on my Thinkpad X61 doesn't
work.  Checking DSDT of X61, many changes were found comparing with
older Thinkpad (eg. X41).  So I made the patches against acpi_ibm(4)
as a workaround so that devd(8) events are handled by event handler in
acpi_ibm(4).

the patches at:
http://people.freebsd.org/~iwasaki/acpi/acpi_ibm-20120615.diff

With the following sysctl setting, now brightness control is working :)

sysctl dev.acpi_ibm.0.events=1
sysctl dev.acpi_ibm.0.handlerevents='0x04 0x10 0x11'

Thanks!