drm/i915: New IRQ management code from Linux

* Move some functions around, they were defined in different files
  than in Linux

* Add some Haswell and Valleyview support code

* Generally reduce differences with Linux 3.8.13
kernel/acpi: Sync acpi_video with FreeBSD.

* Add LCD brightness control notify handler.

* Add support for "cycle" and "zero" events for LCD brightness control.

* Fix recognition of video outputs that use the standardized device
  ID scheme in ACPI 3.0 and set bit 31 at the same time (such as certain
  Dell laptops).
nrelease: Verify that $DPORTS_TREE indeed exists as a directory.

Also, if it exists, output its name so it can be looked up in the
logfile (in case there might have been a typo when overriding the
default).