prime features

[Dave Airlie]

Okay I thought I was finished for 1.18, but PRIME has been missing
a couple of features and I'd thought I'd better implement them.

The first two patches, are reposts of the output master support
for -modesetting/glamor.

The second two patches add reverse prime support to -modesetting,
this is a feature the DDXes already support so it would be good
to have modesetting in the same playing field, it adds a glamor
interfaace to back a pixmap instead of creating a new one.

Patch 5: adds HW cursor support for PRIME, up until now if we
are in a prime situation we used sw cursors, since the USB
devices don't have HW cursors, we want to be able to dynamically
work this out, but it also means we should use the HW cursors
on secondary GPU outputs.

Patch 6: adds PRIME rotation support, this has been one the RFE
/TODO list for a while, it has to do the support at the DIX
level, not in the DDX code due to a) some drivers not using the
DDX code, b) avoiding extra copies. This breaks ABI, but adds
a #define so people know.

Please review,
Dave.