- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

Fix the incomplete conversion from atomic_t to long for test_bit().

Clarify confusions between atomic_t and bitmap. Fix bitmap operations
accordingly.

- Remove test_and_set_bit() macro. It is unused since r255037.
- Relax atomic_read() and atomic_set() macros. Linux does not require any
memory barrier. Also, these macros may be even reordered or optimized away
according to the API documentation:

https://www.kernel.org/doc/Documentation/atomic_ops.txt

drm: Update drm_atomic.h, now that projects/atomic64 is in HEAD

Submitted by: jkim@

Add the code for new Intel GPU driver, which supports GEM, KMS and
works with new generations of GPUs (IronLake, SandyBridge and
supposedly IvyBridge).

The driver is not connected to the build yet.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week