Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC r258779,r258780,r258787,r258822:

Fix undefined behavior: (1 << 31) is not defined as 1 is an int and this
shifts into the sign bit. Instead use (1U << 31) which gets the
expected result.

Similar to the (1 << 31) case it is not defined to do (2 << 30).

This fix is not ideal as it assumes a 32 bit int, but does fix the issue
for most cases.

A similar change was made in OpenBSD.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

drm/radeon: Import the Radeon KMS driver

This driver is based on Linux 3.8 and a previous effort by kan@.

More informations about this project can be found on the FreeBSD wiki:
https://wiki.freebsd.org/AMD_GPU

The driver is split into:

sys/dev/drm2:
The driver sources.

sys/modules/drm2/radeonkmw:
The driver main kernel module's Makefile.

sys/modules/drm2/radeonkmsfw:
All firmware kernel module Makefiles. There's one directory and one
Makefile for each firmware.

sys/contrib/dev/drm2/radeonkmsfw:
All firmware binary sources.

tools/tools/drm/radeon
Tools to update firmwares or regenerate some headers.

Merging the driver to FreeBSD 9.x may be possible but not a priority for
now.

Help from: kib@, kan@
Tested by: avg@, kwm@, ray@,
Alexander Yerenkow <yerenkow@gmail.com>,
Anders Bolt-Evensen <andersbo87@me.com>,
Denis Djubajlo <stdedjub@googlemail.com>,
J.R. Oldroyd <fbsd@opal.com>,
Mikaël Urankar <mikael.urankar@gmail.com>,
Pierre-Emmanuel Pédron <pepcitron@gmail.com>,
Sam Fourman Jr. <sfourman@gmail.com>,
Wade <wade-is-great@live.com>,
(probably other I forgot...)
HW donations: kyzh, Yakaz