Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

drm: Update the device-independent code to match Linux 3.8.13

This update brings few features:
o Support for the setmaster/dropmaster ioctls. For instance, they
are used to run multiple X servers simultaneously.
o Support for minor devices. The only user-visible change is a new
entry in /dev/dri but it is useless at the moment. This is a
first step to support render nodes [1].

The main benefit is to greatly reduce the diff with Linux (at the
expense of an unreadable commit diff). Hopefully, next upgrades will be
easier.

No updates were made to the drivers, beside adapting them to API
changes.

[1] https://en.wikipedia.org/wiki/Direct_Rendering_Manager#Render_nodes

Tested by: Many people
MFC after: 1 month
Relnotes: yes

drm: Fix a call to free(9) with an incorrect malloc type

While here, the call to free(9) is moved to drm_global.c, near the
initial malloc(9).

Reviewed by: Konstantin Belousov (kib@)

drm_global.c: Destroy sx in drm_global_release()

This fixes a build error at the same time (unused variable "item"), if
the kernel is compiled without INVARIANTS.

Reported by: Hartmann, O. <ohartman@zedat.fu-berlin.de> (build error)
Reviewed by: Konstantin Belousov (kib@)

Import the drm_global references helpers.

Sponsored by: The FreeBSD Foundation
MFC after: 1 month